So it was job done for Andy Murray - and in some style. Aside from dropping his serve once towards the end of the third set, the Briton looked razor-sharp throughout.
He'll face a tougher challenge in Tomas Berdych in the next round on Thursday, but if he can continue this form and carry this momentum, the 27-year-old will be a tough man to beat.
Thanks for your company. It's been a pleasure. Until next time, it's good morning from me. Bye!
Post update
If you want to catch up on the match and can't face going through this live text commentary, I'd suggest reading Piers Newbery's developing report.
Post update
That's all the singles play done and dusted for the day, with Andy Murray next in action on Thursday.
But before that, what a day of tennis we have in store tomorrow. Venus Williams will continue her renaissance when she takes on fellow American Madison Keys at 00:00 GMT.
She'll be followed on court by her sister and top seed Serena, who plays 11th seed Dominika Cibulkova. Defending champion Stan Wawrinka follows against Kei Nishikori.
And four-time Australian Open Novak Djokovic headlines the night session when he takes on eighth seed Milos Raonic.
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Alice Stainer: Sounds like Murray was 'lobbing' grenades at Kyrgios. Great stuff. Next match could be a spicy one given Vallverdu connection...
Catie Craig: So thoughtful of Andy Murray finishing in time for me to get to my gym class. Plus great post match on court interview.
Matthew Fowell: Having now beaten two Australians, Murray is not exactly ingratiating himself with the partisan crowd!
"I don't know who will win between Murray and Berdych - it's a tricky one to call.
"Murray has got to serve as well as he did today. Berdych hits the ball well, he's higher risk, he hits the ball flatter and Andy has got that safety element.
"But Berdych hasn't won a Slam so I suppose that gives the edge to Murray. One thing is for sure...it's going to be a ripper."
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Andy Murray on his semi-final against Tomas Berdych: "It will be another tough match, Thomas is another big, big hitter of the ball. He has played extremely well throughout the tournament - I don't think he has lost a set yet. It is going to be tricky."
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Getty ImagesCopyright: Getty Images
Andy Murray on the home support for Nick Kyrgios in Melbourne: "Understandably Nick got great support from this crowd and to play in front of packed court, with some wonderful players watching on, is wonderful. It's a privilege. Hopefully I can keep it going in next round."
Murray through to the semi-finals
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Murray's combination of a higher winner count of 48 to Kyrgios' 36 and low unforced error total of 28 to Kyrgios' 38 was the story of the match today. Meanwhile, the Briton had nine break point opportunities, taking three, while his Australian opponent managed just one from two - and they didn't come until the third set.
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
APCopyright: AP
Andy Murray: "It was a tricky match pretty windy, tough for both of us. I had to start as quickly as possible, I knew what he is capable of and didn't underestimate him. Nick is a huge hitter so I tried to keep the ball out of his reach. I played a slightly different style tonight - and thankfully it worked."
"Great performance from Andy Murray. He kept the pressure on Kyrgios, he served well and didn't give him many short balls. By and large he didn't let him get into the match. In the end, the groundstrokes were really dominant. Murray is still going to be fresh for the semi-final - he has only dropped one set - that's what he needs at this stage of the tournament."
Murray through to the semi-finals
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
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Andy Murray throws his sweatbands into the crowd, waving to the fans in appreciation and then applauding Kyrgios as he walks off court. The 27-year-old will now contest his fifth Australian Open semi-final and 15th semi-final at a Grand Slam. Tomas Berdych, who beat Rafael Nadal earlier today and who recently hired Murray's ex-coach Dani Vallverdu, will be his opponent in the last four.
Game, set and match
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Getty ImagesCopyright: Getty Images
After a brave performance, Kyrgios looks to have run out of gas as a backhand from Murray sails past for 15-15. The Australian sprays the ball into the tram-lines in the next and then finds himself facing match point as Murray hits a forehand winner. And It's another forehand winner, this time down the line, that seals it. Murray wins.
"Two very good points by Andy Murray to finish that off. Even champions lose concentration but what they do is bounce back really quickly from a setback."
Murray breaks
*Murray 6-3 7-6 (7-5) 5-3 Kyrgios
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Kyrgios looks reborn, bouncing up from his seat at the changeover and racing to a 30-0 lead on his serve.
But Murray snatches the next and then delivers the kind of defence which has seen him win the big matches, stretching this way and that, doing anything and everything to get the ball back before conjuring up some magic with a delicate top-spin pass which skips past Kyrgios. Back to 30-30.
Soon we're at deuce, the crowd chanting in between points in support of their man Kyrgios. But they can do nothing to help Kyrgios stop a whipping forehand pass glide by for break point.
Murray drags Kyrgios from side-to-side before the Australian can run no more and dumps a forehand into the net. Murray breaks. He will now serve for the match.
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Joel, Pembrokeshire: Wasn't expecting that from Kyrgios! Wow! This could be a long, and brilliant match!
"Kyrgios is still alive - that was a poor game from Murray. The drop shot was a shocker, he clunked it barely halfway into the net. It has got Kyrgios back into the match and this is exactly what Murray didn't want. He got himself into position, quietened the crowd and had Kyrgios kicking himself."
Kyrgios breaks
Murray 6-3 7-6 (7-5) 4-3 Kyrgios*
There's an opening for Kyrgios as he gets 15-30 on the Murray serve before play is disrupted while a ball girl retrieves an insect which is flittering around the Briton's feet on the service line.
The Briton wins the next point, but then gifts Kyrgios his first break point of the match by spraying a backhand wide! But the Australian frames his next return, looping the ball high in the air.
It lands in and Krygios chases it to the net putting his racquet out in front of him to shield himself from the incoming smash. Murray does well not to hit the Australian, putting the ball away to win the point.
But a forehand error from Murray is followed by a backhand in the net and Rod Laver Arena erupts. Krygios breaks. He's not done yet.
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Piyal: Andy Murray playing fantastic. Looking fit and firing and playing great on the big points. Come on Andy!!!
"That's an outrageous defensive lob which somehow got over Kyrgios. Murray did the right thing and followed it into net. Murray has hit three of the best lobs I've seen in my life during this match.
"But Kyrgios has primarily lost that break because he was screwing around with that between-his-legs shot into the net at 40-30. He has got to realise he can't do that against these guys."
Murray breaks
*Murray 6-3 7-6 (7-5) 4-2 Kyrgios
Murray gets his first real chance in this set as he hauls Krygios back from 40-0 up to deuce and then gets a break point when the Australian double-faults. Could this be the end for the 19-year-old? Oh no! A big forehand saves it.
Another break point. But that's saved, too. Now a third for the Briton. Kyrgios tries a shot between-the-legs as he scrambles to keep himself in play, but unlike the winner he hit against Rafael Nadal at Wimbledon, Murray puts this one way.
Murray breaks and is now just two games away from a semi-final with Tomas Berdych.
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Murray 6-3 7-6 (7-5) 3-2 Kyrgios*
Kyrgios calls for his towel after putting away a crisp forehand volley to win the first point on the Murray serve. The Briton then goes long and Kyrgios has 0-30! You have to go back to the early part of the first set to find when that last happened.
Can he get his first break point of the match? No he can't. Murray fires in four first serves and rattles off the points to hold. Kyrgios raises his racquet as if to smash it to the ground but then thinks better of it.
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Marc Egan: Top class performance here from Andy on Rod Laver!
And top class patriotism from you, Marc...
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*Murray 6-3 7-6 (7-5) 2-2 Kyrgios
Lovely stuff from Kyrgios in this service game, the Australian dictating the points from the off and keeping Murray running for ultimately no reward. The 19-year-old wins the game to love.
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Murray 6-3 7-6 (7-5) 2-1 Kyrgios*
Murray wipes his brow after firing his sixth ace of the match to move 40-0 clear and then follows it up with a crunching forehand winner. Still no break point for Kyrgios.
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Andrew Neill: With those exquisite lobs has this match now gone over Kyrgios' head too?
Lawrence Garner Allen: A comeback from here would truly show the world that Kyrgios is the 'real deal'. Against Andy in this form, not today I'm afraid.
Nick Wall: This is as good as Murray's ever played - even better than when he won Wimbledon. 3 finals here, I think it'll be 4th time lucky
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*Murray 6-3 7-6 (7-5) 1-1 Kyrgios
Kyrgios isn't going down without a fight, the Australian wrapping his racquet around the ball to send it spinning out of court for his 16th winner of the match. Murray shanks a backhand in the next and we're level in the third set.
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Murray 6-3 7-6 (7-5) 1-0 Kyrgios*
Right then, what has Kyrgios got left? If the Australian is to progress to the next round, he will have to win his third five-setter in five matches.
A crisp forehand return that glides over the net is about as good as it gets for the Australian as Murray cruises through another service game. Big service game for Kyrgios coming up. Very big.
"The two lobs from Murray were the difference in that tie-break. They were great lobs, one on the forehand side, one on the backhand side.
"Kyrgios is not easy to get over the top of, he is a big man and has a great leap. The winner was a perfect lob - it had that much top spin, height and it dropped so quickly that Kyrgios didn't even bother turning to chase.
"I'd imagine that it is too much of an ask for Kyrgios to come back from two sets down against someone of the calibre of Andy Murray."
Game and second set
Murray 6-3 7-6 (7-5) Kyrgios
Getty ImagesCopyright: Getty Images
Kyrgios clenches his fist and runs towards the crowd roaring with delight after forcing Murray into a backhand error. He has the mini-break! But his joy is short-lived as Murray conjures up arguably the topspin lob of the tournament that Kyrgios doesn't even bother trying to catch.
Now it's Murray who is fist-pumping as he moves into a 5-4 lead. It looks like he's consolidated the break when a second serve is called in, but Kyrgios challenges and wins it for 5-5.
Clever serve from Murray, catching Kyrgios out, to give him set point. And he takes it with another sensational lob. Murray leaps in the air, clenching his fist and shooting a glance to his box. That was a huge point and leaves Kyrgios facing a long way back.
Getty ImagesCopyright: Getty Images
Tie-break
Murray 6-3 6-6 (3-3) Kyrgios
Murray with the early advantage, getting the mini-break on the first point and backing it up with a big serve. But Kyrgios pulls off an exquisite volley as he charges to the net to snatch the mini-break back. We're level at 3-3 at the change of ends.
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Murray 6-3 6-6 Kyrgios*
Piers Newbery
BBC Sport at Melbourne Park
"Kyrgios and the crowd have picked up a bit as we head to a tie-break. The next few minutes could determine whether we have a long morning/evening or it is done and dusted in 40 minutes."
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Stuart Lesser: Murray doing exactly what he needs to here, pressure Kyrgios on his serve and keep it tight on his own serve.
Tie-break
Murray 6-3 6-6 Kyrgios*
Another ace from Murray, his fifth of the match, and we're heading for a tie-break, folks!
"A very cheeky shot from Nick Kyrgios - that was a tough one to do, the inside out. He learned that one from his mate Bernard Tomic! It was very like what Tomic does. A great shot."
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*Murray 6-3 5-6 Kyrgios
A couple of surprising misses from Murray to gift Kyrgios a 30-0 lead on serve. Kyrgios has certainly settled into this match a lot more and is asking more questions of Murray, the sixth seed and two-time Grand Slam champion.
Kyrgios then gets the crowd on its feet as he fires an audacious angled cross-court forehand, the ball just clearing the net and landing in to seal the game. The Australian raises his arms to take in the applause. He's loving it.
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Murray 6-3 5-5 Kyrgios*
EPACopyright: EPA
Kyrgios goes big on the first point, but his forehand goes long. Still, it signals his intention for the game. The crowd love it and it's clear they're starting to get more involved in this match. Unfortunately, nothing really goes right for Kyrgios as Murray wins the next three points in quick succession to win the game.
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Paul, Glasgow: I'm not convinced Kyrgios will do much damage to Andy. He is another player who thumps in aces and hits the ball as hard as he can - there is no thought process. Andy at least analyses his shots and watches the other player to work out their game!! I could be wrong because Andy often has a lull in his game and let's other players back in.
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*Murray 6-3 4-5 Kyrgios
Kyrgios sees Murray's love service game and fires in one of his own to move one game clear again. Murray must serve to stay in the set in what will be the first bit of any real pressure he's faced all match.
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Murray 6-3 4-4 Kyrgios*
Murray continues to ease through his service games with minimal pressure and we're back level in the second set. Still not a single break point for Kyrgios.
Djokovic-Murray final?
Two players led the way in our vote to see who you think will win the men's Australian Open title.
Four-time champion Novak Djokovic polled 53.1%, with three-time finalist Murray on 37.6% and the rest, frankly, nowhere.
"Andy Murray has good touch and control but there he hit three of the worst drop-shots he's hit in his life. They were too floaty. Murray wags his finger at himself, he knows it was the wrong shot."
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*Murray 6-3 3-4 Kyrgios
Kyrgios raises his arms in the air and asks himself "What was that?" - or something along those lines - after dumping a tame forehand into the net.
It gives Murray a sniff of a chance at 30-30, but Kyrgios reads the next two points really well and finishes the game with a forehand winner that leaves Murray shaking his head in disappointment.
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Andrew Murfin, Isle of Man, via text: Murray is far more controlled than Kyrgios. For all his hustle and bustle the Aussie will blow himself out. Expect a close second set then 6-1 in the third and final set.
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Murray 6-3 3-3 Kyrgios*
EPACopyright: EPA
Murray uses his serve out wide time and time again to drag Kyrgios out of court and is rewarded with a service hold to love. Pressure back on Kyrgios.
"Kyrgios has settled into the match, cutting out the unforced errors in this second set. His game plan is just starting to come together, pushing Murray about at the back of the court, working his opponent to hit the short ball and then find the winner."
Post update
*Murray 6-3 2-3 Kyrgios
Good stuff from Kyrgios in this game, the Australian's forehand starting to look a lot more potent. His serve is more consistent, too, and he takes some pressure off with an easy service hold. This set is a lot closer, that's for sure, but I'd say Murray still has the momentum.
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Richie Macca: Murray needs to show some class and just usher Kyrgios out of the tournament without a peep. Silence the crowd.
Post update
Murray 6-3 2-2 Kyrgios*
Hope for Kyrgios - and indeed the crowd - as he takes the first point on the Murray serve. And even more hope when he forces 30-30, to the delight of an Australian sextet who chant the 19-year-old's name.
But the chance disappears within seconds as Murray flies through the next two points to seal the game. A few minor chances for Kyrgios, but still no break points.
"Andy Murray is fit - that's the main thing for him going into 2015. He's in good shape and I think this will be a good year for him. I wouldn't be surprised if we see him lifting the Australian Open trophy in a few days' time."
Post update
*Murray 6-3 1-2 Kyrgios
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Danger for Kyrgios who finds himself staring down the barrel of 0-30. The Australian's serve comes to his rescue, two aces helping him to game point before Murray forces deuce and then gets his first break point of the set with a crunching backhand winner.
Kyrgios hits a forehand winner on the next but Murray challenges it. It's in! The crowd love it. We're back to deuce. And deuce again. And a third deuce. It's nip-and-tuck. Murray countering everything Kyrgios has to offer.
But the Australian summons some resolve and powers through to seal the game. Boy, it's hard going on his serve.
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Gary Devine, via text: Murray to win in three - physically and mentally too strong for Kyrgios.
Post update
Murray 6-3 1-1 Kyrgios*
"Come on," roars Kyrgios, the Australian starting to get more animated as he reaps the rewards for attacking a Murray second serve.
Murray hauls it back to 30-15 and that's followed by a terrific exchange at the net, the pair trading drop shots and volleys before Murray gets one past Kyrgios.
The Australian bravely chases it down, but frames it high into the crowd. And what a catch by one of the spectators! Kyrgios manages a smile, but seconds later, the game is lost and Murray is level.
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*Murray 6-3 0-1 Kyrgios
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Kyrgios has come out fighting, the Australian looking looser and freer with his shots and it's paying off. The 19-year-old blitzes to a 40-0 lead, including knocking a volley from the back of court back in play for a winner despite the ball looking like it was going out.
Murray snatches the next two points, but Kyrgios' serve comes to the rescue to clinch the game. Kyrgios roars with satisfaction. The crowd respond. You feel the Australian needs to get more involved in this match and take advantage of the home support.
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Sebastian Jenkins: Murray looks the part again on court. He looks like the next Australian Open champion to me.
Alan Peevers: I think Berdych will beat Murray. He's on fire and he has a new coach who knows everything about Andy.
"The feet haven't been moving for Kyrgios yet, he's made way too many unforced errors. Now he needs to come out swinging, get a break, get the crowd excited.
"Murray's job is to keep putting the ball deep and say 'come on young fella, this is a different match against me at a Grand Slam'.
"Kyrgios hasn't really beaten anyone good yet - and certainly not anyone who is anywhere near as good as Andy Murray."
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Piers Newbery
BBC Sport at Melbourne Park
"An audible obscenity, gesturing at the ball kids, a few flashing winners... plenty of the trademark Kyrgios features on show but he doesn't carry quite the same swagger as he's being clinically dismantled on a cold and blustery evening. Murray has quietened the crowd, a classic away tie performance."
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Getty ImagesCopyright: Getty Images
The Rod Laver Arena's PA system blasts out a bit of cheesy pop as the players have a breather - but it isn't one of the hits sung by this man. Underneath the black baseball cap and sunglasses - that classic celebrity disguise - is One Direction heart-throb Niall Horan.
This match is only going in One Direction - in the way of Andy Murray....
Game and first set
Murray 6-3 Kyrgios*
Murray breezes through another service game for the loss of just a single point to seal the game as Kyrgios bounces his racquet on the ground in frustration.
"Kyrgios has got a great ability to hang in there on serve in big matches, saving set points. Now the pressure is back on Murray."
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*Murray 5-3 Kyrgios
Kyrgios finds himself in yet more bother at 15-30 down, but Murray sprays a couple of balls wide to hand the Australian game point.
A short looping return is there for the taking for Kyrgios, but he shanks it long. And makes another hash of the next point to give Murray set point. That goes wanting and Kyrgios regroups to reach game point, dipping down to pick up a low ball at the net.
Murray continues with his tactic of keeping the ball low and throwing in the drop shots appears to work, as 6ft 4ins Kyrgios struggles to get down to the ball and the Briton gets another set point.
Again, Kyrgios saves it and then rattles off three points, finishing with a forehand winner, to seal the game and force Murray to serve for the set.
You'd have to say Murray is still in control, mind.
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Murray 5-2 Kyrgios*
Murray mixing it up brilliantly on his serve, keeping Kyrgios guessing on the return. The result is another comfortable service hold and the Briton is now just one game away from the first set after just 20 minutes of play.
Murray breaks
*Murray 4-2 Kyrgios
APCopyright: AP
The Aussie fans are in full song on Rod Laver Arena, cheering Kyrgios' every point. Early on in this game, they have plenty to smile about as Kyrgios races to 30-0, but a couple of errors gift Murray his first break point of the match.
Pressure? What pressure? Kyrgios hammers an ace out wide to force deuce. But back comes Murray, forcing the Australian into an error. Another break point. This time, Kyrgios can't pull out a big serve. Murray jumps on it, dominates the point and watches on as Kyrgios sprays wide. Murray breaks.
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Laura Lambert: Murray made it look easy in Toronto and although Kyrgios will be buzzing in front of home crowd, and the opportunity to make a Grand Slam semi-final, it's Murray in three for me.
Post update
Murray 3-2 Kyrgios*
Kyrgios berates himself as he watches a regulation forehand get buried in the net but he can have another to be angry about in the next point as another crunching serve from Murray seals the game. The Briton cruising on his serve at the moment.
Big-match nerves
Kyrgios showed his nerves ahead of the quarter-final, as you can see in this Vine video. (It's a social media thing)
"Kyrgios is getting pumped. He's got nothing to lose, can bide his time and with a big serve like that he can be patient and let the more experienced guy get a little tight."
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*Murray 2-2 Kyrgios
Kyrgios looks imposing at the net, the 6ft 4ins Australian putting away a smash on his way to a 40-0 lead. But back comes Murray, who is starting to get a racquet on a few more returns. A sniff of pressure at 40-30 but Kyrgios snuffs it out, roaring with satisfaction as he clinches the game.
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DW, via text: Re. Callum Johnstone (see 08:34). Not sure I agree with all the Murray-Djokovic inevitability talk; we said that about Djokovic at Oz and US Opens last year...and did you see Berdych today? Pretty impressive...
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Murray 2-1 Kyrgios*
EPACopyright: EPA
Blink and you'll miss it. Murray races through his service game, winning his eighth consecutive point on serve, to clinch the game. A solid start from Murray and one which is much stronger than that against Dimitrov in the last round.
"They were nice, sliced serves straight down the middle from Andy Murray. Over the lower part of the net, a bit of curve, you don't have to hit them at 200kph. What Murray did was exactly right - take a bit off it and hit the target."
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Post update
Murray 1-0 Kyrgios* (*denotes the next to serve)
We're off and what a start for Kyrgios, who latches onto a short ball and whips it down the line for 0-30. But that's as good as it gets for the Australian, who has no answer to some supreme serving from Murray. The Briton throws in a couple of aces to dig himself out of trouble and get the first game on the board.
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Alex Haworth: When did sportsmen decide that wearing headphones before the start of the match was cool? Looks ridiculous.
Andrew Neill: Kyrgios has played very well up to now but it'd still be a shock for a man with only one ATP tour win to triumph today. Murray in four.
Callum Johnstone: Murray vs Novak seems inevitable now doesn't it….?
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The warm-up is over. Let's. Play. Tennis.
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@AUSOPEN/TwitterCopyright: @AUSOPEN/Twitter
These four blokes are a regular sight at Andy Murray matches, serenading the British number one with their ditties. But they face a tough task to out-sing the partisan Aussie crowd tonight. That said, I'm sure they'll give it a go...
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Murray has stuck with his all-black ensemble completed with luminous green trainers for this match while Kyrgios has gone brighter, the Australian sporting a white top with a splattering of fluorescent yellow. Crikey, it's so bright, you could probably spot him from space.
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David Law
BBC Radio 5 live sports extra commentator
"Nick Kyrgios isn't used to this - he just followed Andy Murray out on to court. He didn't know that he had to wait for his name to be called!"
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Andy Murray strolls out onto Rod Laver Arena, giving the crowd a wave as he is introduced. Kyrgios was held back by one of the stewards, though. He was in his own world, listening to his music. Seconds later, he is given the go-ahead and is met with a huge roar from an expectant crowd.
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The players are limbering up in the tunnels within the Rod Laver Arena. Murray is smiling, he's looking super relaxed. Behind him, Kyrgios has his headphones on and has a very stern look on his face. We're minutes away, folks.
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David Law
BBC Radio 5 live sports extra commentator
"All logic tells me that Andy Murray will be mentally too strong, too tight in his game. I watched their previous meeting in Toronto and it was the same on that occasion.
"It will be closer this time because I think Kyrgios is in a better place psychologically.
"The first set is vital. I don't think we will see him beat Murray from two sets down. He needs to get this place jumping from the off.
"Kyrgios is box office, he makes tennis enjoyable, he makes people who don't watch tennis watch tennis."
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David McQueen: Living in Sydney, expecting a ribbing if Murray loses! Fancy Andy in four though. Tactically and defensively too good at this stage.
Andrew Priestley: I'm not expecting to be very productive in work this morning while Murray vs Krygios is going on! A simple 3-setter please! #bbctennis
(We assume Andrew is supporting his namesake)
Post update
But if Kyrgios is triumphant, the 19-year-old will become the first Australian man to reach the Australian Open semi-finals since Lleyton Hewitt in 2005.
And at 19 years and 280 days, he will also become the second youngest man in the Open Era to reach the last four in Melbourne. Mats Wilander - yep it's the Swede again - holds that record at 19 years and 111 days in 1983.
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If Murray is successful today, he will reach the semi-finals in Melbourne for the fifth time in his career. It'll be his 15th Grand Slam semi-final, overtaking Mats Wilander into 12th place on the list of most Grand Slam last four appearances.
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Piers Newbery
BBC Sport at Melbourne Park
"Murray has won his last 10 matches against home players at Grand Slams and has a 10-0 record against Australians, so that's all stacked up pretty well for him.
"He also has years of experience playing on Rod Laver Arena, while Kyrgios will be making his competitive debut there - prompting a few barbed words from commentators towards the schedulers over the last week.
"The general view appears to be that Murray's return game will eventually blunt the Australian's huge serve, while big-match fitness and experience also favours the Scot. Kyrgios was heard on the practice court earlier shouting, "Why am I so nervous?" It's anyone's guess what he will bring tonight."
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Getty ImagesCopyright: Getty Images
Murray has never lost at the Australian Open to a player ranked as low as world number 53 Kyrgios. If you were wondering, Juan Ignacio Chela - then ranked 51st - is the lowest-ranked player to defeat Murray in Melbourne. That was on Murray's Australian Open debut in 2006.
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We're expecting the players on court shortly, with BBC Radio 5 live sports extra already up and running. You can listen to commentary via the 'Live Coverage' tab at the top of the page.
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Getty ImagesCopyright: Getty Images
Nick Kyrgios hit the headlines with that stunning victory over Rafael Nadal at Wimbledon last year, but in the following round, he went down in four sets to Milos Raonic. This time around, the world number 53 feels better prepared.
"I think I'll be pulling up better than I did at Wimbledon," he says. "I know what to expect now, what I am going to be feeling, especially after a five-set match like that.
"It's massive confidence being 19 knowing that you can last matches like that. It's massive."
Elaine McCallum: #AusOpen all the way from Scotland. Go Andy Murray.
Where are you planning on following Andy Murray's quest for a semi-final place from? Send us your tweets and photos to #bbctennis.
The tale of the tape
Murray v Kyrgios (08:15 GMT)
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The players have met just once on tour, with Murray winning in straight sets in Toronto last summer. The Briton also won the set they played at the International Premier Tennis League (IPTL) exhibition in India two months ago.
"There were some things that I did in that match [in Toronto] which I believe will work on Tuesday," says Murray. "So I've learnt stuff from playing against him there and at the IPTL and watching him a bit, stuff that I feel I can use and exploit in his game."
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Piers Newbery
BBC Sport at Melbourne Park
"The atmosphere has been a bit flat around Melbourne Park so far today, possibly a collective hangover from Australia Day on Monday and possibly because of the autumnal 17C temperature and chilly breeze.
"There is little chance of things remaining calm as we head into the main event of the day, however. The match has been hyped from breakfast time this morning with the host broadcaster's 'Countdown To Kyrgios' clock on screen, and most of the spectators look like they decided not to change out of their Australia Day gear."
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At Wimbledon, Murray has a home crowd who will cheer his every shot and help carry him through the toughest moments.
Kyrgios will have that benefit of the home support but Murray is confident he'll be able to deal with the atmosphere.
"Obviously the crowd will be right behind him, understandably so," said the 27-year-old. "They're going to watch him play a lot of matches like this over the next 10, 15 years probably, and that's just something that I'll have to deal with in my way.
"I've played a lot of matches. I've played in the French Open against French players where the crowd can be very difficult. I've experienced it before, so hopefully I'll deal with it well."
It's been harder work for Nick Kyrgios, who has had to come through two five-setters, including a thriller in the last round against Andreas Seppi, who was Roger Federer's conqueror.
But his success has made him the first home player for 10 years to reach the Australian Open men's quarter-finals. "When I saw I had finally won the match it was incredible. It was the best feeling I ever had," said Kyrgios. "It's crazy."
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It was pretty much plain sailing for Murray on his way to the last eight, with only Grigor Dimitrov providing any real resistance.
The Scot was delighted with the way his body held up in the closing stages of that tussle, having struggled at times on his return from back surgery in 2014.
"My body allowed me to play that way for the whole duration of the match," said Murray. "I didn't feel tired. I felt fresh. My back felt good. I wasn't feeling stiff at all."
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Who is Nick Kyrgios? He's the chap who pulled off a between-the-legs winner against Rafael Nadal on Wimbledon's Centre Court last year.
And he's continued making a name from himself ever since.
"Smashed racquets, audible obscenities, conversations with the crowd, "cocky" on-court interviews, all among a blizzard of winners and aces - it has been impossible to take your eyes off him at Melbourne Park," writes BBC Sport's Piers Newbery.
Read more about him the 19-year-old from Canberra - and watch that between-the-legs winner - here.
Andy Murray and Nick Kyrgios headline the night session, with the players due on court at 08:15 GMT.
We've got a two-pronged attack of coverage for you this morning, with BBC Radio 5 live sports extra up and running with their build-up ahead of live commentary.
You can give that a listen by clicking the 'Live Coverage' tab at the top of this page and, er, hitting play.
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And that's where our focus moves, with Britain's Andy Murray bidding to win his first Australian Open title, after three final defeats.
Standing in his way is Nick Kyrgios, the 19-year-old phenomenon who has gripped the world of tennis and his home nation with his raw talent, wacky t-shirts and zig-zig designs carved into his hair.
Can the young pretender beat the two-time Grand Slam champion in the quarter-finals?
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So another seed bit the dust this morning, as Tomas Berdych completely outplayed Rafael Nadal, the 2009 Australian Open champion.
There was a bit of a wobble in the third set for Berdych, but who can blame him? The Czech was on the cusp of ending a 17-match losing streak which goes back to 2006.
But in the end, Berdych got across the line for a victory he thoroughly deserved.
His reward? A semi-final match against Britain's Andy Murray or Australian's rising star Nick Kyrgios, dubbed "Wild Thing" by the host broadcaster.
Live Reporting
Lawrence Barretto
All times stated are UK
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Latest PostPost update
So it was job done for Andy Murray - and in some style. Aside from dropping his serve once towards the end of the third set, the Briton looked razor-sharp throughout.
He'll face a tougher challenge in Tomas Berdych in the next round on Thursday, but if he can continue this form and carry this momentum, the 27-year-old will be a tough man to beat.
Thanks for your company. It's been a pleasure. Until next time, it's good morning from me. Bye!
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If you want to catch up on the match and can't face going through this live text commentary, I'd suggest reading Piers Newbery's developing report.
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That's all the singles play done and dusted for the day, with Andy Murray next in action on Thursday.
But before that, what a day of tennis we have in store tomorrow. Venus Williams will continue her renaissance when she takes on fellow American Madison Keys at 00:00 GMT.
She'll be followed on court by her sister and top seed Serena, who plays 11th seed Dominika Cibulkova. Defending champion Stan Wawrinka follows against Kei Nishikori.
And four-time Australian Open Novak Djokovic headlines the night session when he takes on eighth seed Milos Raonic.
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Alice Stainer: Sounds like Murray was 'lobbing' grenades at Kyrgios. Great stuff. Next match could be a spicy one given Vallverdu connection...
Catie Craig: So thoughtful of Andy Murray finishing in time for me to get to my gym class. Plus great post match on court interview.
Matthew Fowell: Having now beaten two Australians, Murray is not exactly ingratiating himself with the partisan crowd!
Murray through to semi-finals
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"I don't know who will win between Murray and Berdych - it's a tricky one to call.
"Murray has got to serve as well as he did today. Berdych hits the ball well, he's higher risk, he hits the ball flatter and Andy has got that safety element.
"But Berdych hasn't won a Slam so I suppose that gives the edge to Murray. One thing is for sure...it's going to be a ripper."
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Andy Murray on his semi-final against Tomas Berdych: "It will be another tough match, Thomas is another big, big hitter of the ball. He has played extremely well throughout the tournament - I don't think he has lost a set yet. It is going to be tricky."
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Andy Murray on the home support for Nick Kyrgios in Melbourne: "Understandably Nick got great support from this crowd and to play in front of packed court, with some wonderful players watching on, is wonderful. It's a privilege. Hopefully I can keep it going in next round."
Murray through to the semi-finals
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Murray's combination of a higher winner count of 48 to Kyrgios' 36 and low unforced error total of 28 to Kyrgios' 38 was the story of the match today. Meanwhile, the Briton had nine break point opportunities, taking three, while his Australian opponent managed just one from two - and they didn't come until the third set.
Player reaction
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Andy Murray: "It was a tricky match pretty windy, tough for both of us. I had to start as quickly as possible, I knew what he is capable of and didn't underestimate him. Nick is a huge hitter so I tried to keep the ball out of his reach. I played a slightly different style tonight - and thankfully it worked."
Game, set and match - Murray
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Great performance from Andy Murray. He kept the pressure on Kyrgios, he served well and didn't give him many short balls. By and large he didn't let him get into the match. In the end, the groundstrokes were really dominant. Murray is still going to be fresh for the semi-final - he has only dropped one set - that's what he needs at this stage of the tournament."
Murray through to the semi-finals
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
Andy Murray throws his sweatbands into the crowd, waving to the fans in appreciation and then applauding Kyrgios as he walks off court. The 27-year-old will now contest his fifth Australian Open semi-final and 15th semi-final at a Grand Slam. Tomas Berdych, who beat Rafael Nadal earlier today and who recently hired Murray's ex-coach Dani Vallverdu, will be his opponent in the last four.
Game, set and match
Murray 6-3 7-6 (7-5) 6-3 Kyrgios
After a brave performance, Kyrgios looks to have run out of gas as a backhand from Murray sails past for 15-15. The Australian sprays the ball into the tram-lines in the next and then finds himself facing match point as Murray hits a forehand winner. And It's another forehand winner, this time down the line, that seals it. Murray wins.
Murray breaks
*Murray 6-3 7-6 (7-5) 5-3 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Two very good points by Andy Murray to finish that off. Even champions lose concentration but what they do is bounce back really quickly from a setback."
Murray breaks
*Murray 6-3 7-6 (7-5) 5-3 Kyrgios
Kyrgios looks reborn, bouncing up from his seat at the changeover and racing to a 30-0 lead on his serve.
But Murray snatches the next and then delivers the kind of defence which has seen him win the big matches, stretching this way and that, doing anything and everything to get the ball back before conjuring up some magic with a delicate top-spin pass which skips past Kyrgios. Back to 30-30.
Soon we're at deuce, the crowd chanting in between points in support of their man Kyrgios. But they can do nothing to help Kyrgios stop a whipping forehand pass glide by for break point.
Murray drags Kyrgios from side-to-side before the Australian can run no more and dumps a forehand into the net. Murray breaks. He will now serve for the match.
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Joel, Pembrokeshire: Wasn't expecting that from Kyrgios! Wow! This could be a long, and brilliant match!
Kyrgios breaks
Murray 6-3 7-6 (7-5) 4-3 Kyrgios*
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Kyrgios is still alive - that was a poor game from Murray. The drop shot was a shocker, he clunked it barely halfway into the net. It has got Kyrgios back into the match and this is exactly what Murray didn't want. He got himself into position, quietened the crowd and had Kyrgios kicking himself."
Kyrgios breaks
Murray 6-3 7-6 (7-5) 4-3 Kyrgios*
There's an opening for Kyrgios as he gets 15-30 on the Murray serve before play is disrupted while a ball girl retrieves an insect which is flittering around the Briton's feet on the service line.
The Briton wins the next point, but then gifts Kyrgios his first break point of the match by spraying a backhand wide! But the Australian frames his next return, looping the ball high in the air.
It lands in and Krygios chases it to the net putting his racquet out in front of him to shield himself from the incoming smash. Murray does well not to hit the Australian, putting the ball away to win the point.
But a forehand error from Murray is followed by a backhand in the net and Rod Laver Arena erupts. Krygios breaks. He's not done yet.
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Piyal: Andy Murray playing fantastic. Looking fit and firing and playing great on the big points. Come on Andy!!!
Murray breaks
*Murray 6-3 7-6 (7-5) 4-2 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"That's an outrageous defensive lob which somehow got over Kyrgios. Murray did the right thing and followed it into net. Murray has hit three of the best lobs I've seen in my life during this match.
"But Kyrgios has primarily lost that break because he was screwing around with that between-his-legs shot into the net at 40-30. He has got to realise he can't do that against these guys."
Murray breaks
*Murray 6-3 7-6 (7-5) 4-2 Kyrgios
Murray gets his first real chance in this set as he hauls Krygios back from 40-0 up to deuce and then gets a break point when the Australian double-faults. Could this be the end for the 19-year-old? Oh no! A big forehand saves it.
Another break point. But that's saved, too. Now a third for the Briton. Kyrgios tries a shot between-the-legs as he scrambles to keep himself in play, but unlike the winner he hit against Rafael Nadal at Wimbledon, Murray puts this one way.
Murray breaks and is now just two games away from a semi-final with Tomas Berdych.
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Murray 6-3 7-6 (7-5) 3-2 Kyrgios*
Kyrgios calls for his towel after putting away a crisp forehand volley to win the first point on the Murray serve. The Briton then goes long and Kyrgios has 0-30! You have to go back to the early part of the first set to find when that last happened.
Can he get his first break point of the match? No he can't. Murray fires in four first serves and rattles off the points to hold. Kyrgios raises his racquet as if to smash it to the ground but then thinks better of it.
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Marc Egan: Top class performance here from Andy on Rod Laver!
And top class patriotism from you, Marc...
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*Murray 6-3 7-6 (7-5) 2-2 Kyrgios
Lovely stuff from Kyrgios in this service game, the Australian dictating the points from the off and keeping Murray running for ultimately no reward. The 19-year-old wins the game to love.
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Murray 6-3 7-6 (7-5) 2-1 Kyrgios*
Murray wipes his brow after firing his sixth ace of the match to move 40-0 clear and then follows it up with a crunching forehand winner. Still no break point for Kyrgios.
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Andrew Neill: With those exquisite lobs has this match now gone over Kyrgios' head too?
Lawrence Garner Allen: A comeback from here would truly show the world that Kyrgios is the 'real deal'. Against Andy in this form, not today I'm afraid.
Nick Wall: This is as good as Murray's ever played - even better than when he won Wimbledon. 3 finals here, I think it'll be 4th time lucky
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*Murray 6-3 7-6 (7-5) 1-1 Kyrgios
Kyrgios isn't going down without a fight, the Australian wrapping his racquet around the ball to send it spinning out of court for his 16th winner of the match. Murray shanks a backhand in the next and we're level in the third set.
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Murray 6-3 7-6 (7-5) 1-0 Kyrgios*
Right then, what has Kyrgios got left? If the Australian is to progress to the next round, he will have to win his third five-setter in five matches.
A crisp forehand return that glides over the net is about as good as it gets for the Australian as Murray cruises through another service game. Big service game for Kyrgios coming up. Very big.
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Murray 6-3 7-6 (7-5) Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"The two lobs from Murray were the difference in that tie-break. They were great lobs, one on the forehand side, one on the backhand side.
"Kyrgios is not easy to get over the top of, he is a big man and has a great leap. The winner was a perfect lob - it had that much top spin, height and it dropped so quickly that Kyrgios didn't even bother turning to chase.
"I'd imagine that it is too much of an ask for Kyrgios to come back from two sets down against someone of the calibre of Andy Murray."
Game and second set
Murray 6-3 7-6 (7-5) Kyrgios
Kyrgios clenches his fist and runs towards the crowd roaring with delight after forcing Murray into a backhand error. He has the mini-break! But his joy is short-lived as Murray conjures up arguably the topspin lob of the tournament that Kyrgios doesn't even bother trying to catch.
Now it's Murray who is fist-pumping as he moves into a 5-4 lead. It looks like he's consolidated the break when a second serve is called in, but Kyrgios challenges and wins it for 5-5.
Clever serve from Murray, catching Kyrgios out, to give him set point. And he takes it with another sensational lob. Murray leaps in the air, clenching his fist and shooting a glance to his box. That was a huge point and leaves Kyrgios facing a long way back.
Tie-break
Murray 6-3 6-6 (3-3) Kyrgios
Murray with the early advantage, getting the mini-break on the first point and backing it up with a big serve. But Kyrgios pulls off an exquisite volley as he charges to the net to snatch the mini-break back. We're level at 3-3 at the change of ends.
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Murray 6-3 6-6 Kyrgios*
Piers Newbery
BBC Sport at Melbourne Park
"Kyrgios and the crowd have picked up a bit as we head to a tie-break. The next few minutes could determine whether we have a long morning/evening or it is done and dusted in 40 minutes."
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Stuart Lesser: Murray doing exactly what he needs to here, pressure Kyrgios on his serve and keep it tight on his own serve.
Tie-break
Murray 6-3 6-6 Kyrgios*
Another ace from Murray, his fifth of the match, and we're heading for a tie-break, folks!
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*Murray 6-3 5-6 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"A very cheeky shot from Nick Kyrgios - that was a tough one to do, the inside out. He learned that one from his mate Bernard Tomic! It was very like what Tomic does. A great shot."
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*Murray 6-3 5-6 Kyrgios
A couple of surprising misses from Murray to gift Kyrgios a 30-0 lead on serve. Kyrgios has certainly settled into this match a lot more and is asking more questions of Murray, the sixth seed and two-time Grand Slam champion.
Kyrgios then gets the crowd on its feet as he fires an audacious angled cross-court forehand, the ball just clearing the net and landing in to seal the game. The Australian raises his arms to take in the applause. He's loving it.
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Murray 6-3 5-5 Kyrgios*
Kyrgios goes big on the first point, but his forehand goes long. Still, it signals his intention for the game. The crowd love it and it's clear they're starting to get more involved in this match. Unfortunately, nothing really goes right for Kyrgios as Murray wins the next three points in quick succession to win the game.
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Paul, Glasgow: I'm not convinced Kyrgios will do much damage to Andy. He is another player who thumps in aces and hits the ball as hard as he can - there is no thought process. Andy at least analyses his shots and watches the other player to work out their game!! I could be wrong because Andy often has a lull in his game and let's other players back in.
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*Murray 6-3 4-5 Kyrgios
Kyrgios sees Murray's love service game and fires in one of his own to move one game clear again. Murray must serve to stay in the set in what will be the first bit of any real pressure he's faced all match.
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Murray 6-3 4-4 Kyrgios*
Murray continues to ease through his service games with minimal pressure and we're back level in the second set. Still not a single break point for Kyrgios.
Djokovic-Murray final?
Two players led the way in our vote to see who you think will win the men's Australian Open title.
Four-time champion Novak Djokovic polled 53.1%, with three-time finalist Murray on 37.6% and the rest, frankly, nowhere.
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*Murray 6-3 3-4 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Andy Murray has good touch and control but there he hit three of the worst drop-shots he's hit in his life. They were too floaty. Murray wags his finger at himself, he knows it was the wrong shot."
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*Murray 6-3 3-4 Kyrgios
Kyrgios raises his arms in the air and asks himself "What was that?" - or something along those lines - after dumping a tame forehand into the net.
It gives Murray a sniff of a chance at 30-30, but Kyrgios reads the next two points really well and finishes the game with a forehand winner that leaves Murray shaking his head in disappointment.
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Andrew Murfin, Isle of Man, via text: Murray is far more controlled than Kyrgios. For all his hustle and bustle the Aussie will blow himself out. Expect a close second set then 6-1 in the third and final set.
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Murray 6-3 3-3 Kyrgios*
Murray uses his serve out wide time and time again to drag Kyrgios out of court and is rewarded with a service hold to love. Pressure back on Kyrgios.
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*Murray 6-3 2-3 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Kyrgios has settled into the match, cutting out the unforced errors in this second set. His game plan is just starting to come together, pushing Murray about at the back of the court, working his opponent to hit the short ball and then find the winner."
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*Murray 6-3 2-3 Kyrgios
Good stuff from Kyrgios in this game, the Australian's forehand starting to look a lot more potent. His serve is more consistent, too, and he takes some pressure off with an easy service hold. This set is a lot closer, that's for sure, but I'd say Murray still has the momentum.
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Richie Macca: Murray needs to show some class and just usher Kyrgios out of the tournament without a peep. Silence the crowd.
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Murray 6-3 2-2 Kyrgios*
Hope for Kyrgios - and indeed the crowd - as he takes the first point on the Murray serve. And even more hope when he forces 30-30, to the delight of an Australian sextet who chant the 19-year-old's name.
But the chance disappears within seconds as Murray flies through the next two points to seal the game. A few minor chances for Kyrgios, but still no break points.
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*Murray 6-3 1-2 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Andy Murray is fit - that's the main thing for him going into 2015. He's in good shape and I think this will be a good year for him. I wouldn't be surprised if we see him lifting the Australian Open trophy in a few days' time."
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*Murray 6-3 1-2 Kyrgios
Danger for Kyrgios who finds himself staring down the barrel of 0-30. The Australian's serve comes to his rescue, two aces helping him to game point before Murray forces deuce and then gets his first break point of the set with a crunching backhand winner.
Kyrgios hits a forehand winner on the next but Murray challenges it. It's in! The crowd love it. We're back to deuce. And deuce again. And a third deuce. It's nip-and-tuck. Murray countering everything Kyrgios has to offer.
But the Australian summons some resolve and powers through to seal the game. Boy, it's hard going on his serve.
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Gary Devine, via text: Murray to win in three - physically and mentally too strong for Kyrgios.
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Murray 6-3 1-1 Kyrgios*
"Come on," roars Kyrgios, the Australian starting to get more animated as he reaps the rewards for attacking a Murray second serve.
Murray hauls it back to 30-15 and that's followed by a terrific exchange at the net, the pair trading drop shots and volleys before Murray gets one past Kyrgios.
The Australian bravely chases it down, but frames it high into the crowd. And what a catch by one of the spectators! Kyrgios manages a smile, but seconds later, the game is lost and Murray is level.
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*Murray 6-3 0-1 Kyrgios
Kyrgios has come out fighting, the Australian looking looser and freer with his shots and it's paying off. The 19-year-old blitzes to a 40-0 lead, including knocking a volley from the back of court back in play for a winner despite the ball looking like it was going out.
Murray snatches the next two points, but Kyrgios' serve comes to the rescue to clinch the game. Kyrgios roars with satisfaction. The crowd respond. You feel the Australian needs to get more involved in this match and take advantage of the home support.
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Sebastian Jenkins: Murray looks the part again on court. He looks like the next Australian Open champion to me.
Alan Peevers: I think Berdych will beat Murray. He's on fire and he has a new coach who knows everything about Andy.
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Murray 6-3 Kyrgios*
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"The feet haven't been moving for Kyrgios yet, he's made way too many unforced errors. Now he needs to come out swinging, get a break, get the crowd excited.
"Murray's job is to keep putting the ball deep and say 'come on young fella, this is a different match against me at a Grand Slam'.
"Kyrgios hasn't really beaten anyone good yet - and certainly not anyone who is anywhere near as good as Andy Murray."
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Piers Newbery
BBC Sport at Melbourne Park
"An audible obscenity, gesturing at the ball kids, a few flashing winners... plenty of the trademark Kyrgios features on show but he doesn't carry quite the same swagger as he's being clinically dismantled on a cold and blustery evening. Murray has quietened the crowd, a classic away tie performance."
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The Rod Laver Arena's PA system blasts out a bit of cheesy pop as the players have a breather - but it isn't one of the hits sung by this man. Underneath the black baseball cap and sunglasses - that classic celebrity disguise - is One Direction heart-throb Niall Horan.
This match is only going in One Direction - in the way of Andy Murray....
Game and first set
Murray 6-3 Kyrgios*
Murray breezes through another service game for the loss of just a single point to seal the game as Kyrgios bounces his racquet on the ground in frustration.
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*Murray 5-3 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Kyrgios has got a great ability to hang in there on serve in big matches, saving set points. Now the pressure is back on Murray."
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*Murray 5-3 Kyrgios
Kyrgios finds himself in yet more bother at 15-30 down, but Murray sprays a couple of balls wide to hand the Australian game point.
A short looping return is there for the taking for Kyrgios, but he shanks it long. And makes another hash of the next point to give Murray set point. That goes wanting and Kyrgios regroups to reach game point, dipping down to pick up a low ball at the net.
Murray continues with his tactic of keeping the ball low and throwing in the drop shots appears to work, as 6ft 4ins Kyrgios struggles to get down to the ball and the Briton gets another set point.
Again, Kyrgios saves it and then rattles off three points, finishing with a forehand winner, to seal the game and force Murray to serve for the set.
You'd have to say Murray is still in control, mind.
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Murray 5-2 Kyrgios*
Murray mixing it up brilliantly on his serve, keeping Kyrgios guessing on the return. The result is another comfortable service hold and the Briton is now just one game away from the first set after just 20 minutes of play.
Murray breaks
*Murray 4-2 Kyrgios
The Aussie fans are in full song on Rod Laver Arena, cheering Kyrgios' every point. Early on in this game, they have plenty to smile about as Kyrgios races to 30-0, but a couple of errors gift Murray his first break point of the match.
Pressure? What pressure? Kyrgios hammers an ace out wide to force deuce. But back comes Murray, forcing the Australian into an error. Another break point. This time, Kyrgios can't pull out a big serve. Murray jumps on it, dominates the point and watches on as Kyrgios sprays wide. Murray breaks.
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Laura Lambert: Murray made it look easy in Toronto and although Kyrgios will be buzzing in front of home crowd, and the opportunity to make a Grand Slam semi-final, it's Murray in three for me.
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Murray 3-2 Kyrgios*
Kyrgios berates himself as he watches a regulation forehand get buried in the net but he can have another to be angry about in the next point as another crunching serve from Murray seals the game. The Briton cruising on his serve at the moment.
Big-match nerves
Kyrgios showed his nerves ahead of the quarter-final, as you can see in this Vine video. (It's a social media thing)
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Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Kyrgios is getting pumped. He's got nothing to lose, can bide his time and with a big serve like that he can be patient and let the more experienced guy get a little tight."
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*Murray 2-2 Kyrgios
Kyrgios looks imposing at the net, the 6ft 4ins Australian putting away a smash on his way to a 40-0 lead. But back comes Murray, who is starting to get a racquet on a few more returns. A sniff of pressure at 40-30 but Kyrgios snuffs it out, roaring with satisfaction as he clinches the game.
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DW, via text: Re. Callum Johnstone (see 08:34). Not sure I agree with all the Murray-Djokovic inevitability talk; we said that about Djokovic at Oz and US Opens last year...and did you see Berdych today? Pretty impressive...
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Murray 2-1 Kyrgios*
Blink and you'll miss it. Murray races through his service game, winning his eighth consecutive point on serve, to clinch the game. A solid start from Murray and one which is much stronger than that against Dimitrov in the last round.
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Murray* 1-1 Kyrgios
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"Kyrgios shows that he has dealt with all this hype pretty well. Australians do tend to get hyped up by tennis!"
Remember you can listen to 5 live Sports Extra by clicking the 'Live Coverage' tab on this page.
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*Murray 1-1 Kyrgios
A super game from Kyrgios, who settles the nerves with a service hold to love. That serve looks pretty tasty and the fast court will suit him.
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Murray 1-0 Kyrgios*
Pat Cash
1987 Wimbledon champion on BBC Radio 5 live sports extra
"They were nice, sliced serves straight down the middle from Andy Murray. Over the lower part of the net, a bit of curve, you don't have to hit them at 200kph. What Murray did was exactly right - take a bit off it and hit the target."
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Murray 1-0 Kyrgios* (*denotes the next to serve)
We're off and what a start for Kyrgios, who latches onto a short ball and whips it down the line for 0-30. But that's as good as it gets for the Australian, who has no answer to some supreme serving from Murray. The Briton throws in a couple of aces to dig himself out of trouble and get the first game on the board.
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Alex Haworth: When did sportsmen decide that wearing headphones before the start of the match was cool? Looks ridiculous.
Andrew Neill: Kyrgios has played very well up to now but it'd still be a shock for a man with only one ATP tour win to triumph today. Murray in four.
Callum Johnstone: Murray vs Novak seems inevitable now doesn't it….?
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The warm-up is over. Let's. Play. Tennis.
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These four blokes are a regular sight at Andy Murray matches, serenading the British number one with their ditties. But they face a tough task to out-sing the partisan Aussie crowd tonight. That said, I'm sure they'll give it a go...
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Murray has stuck with his all-black ensemble completed with luminous green trainers for this match while Kyrgios has gone brighter, the Australian sporting a white top with a splattering of fluorescent yellow. Crikey, it's so bright, you could probably spot him from space.
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David Law
BBC Radio 5 live sports extra commentator
"Nick Kyrgios isn't used to this - he just followed Andy Murray out on to court. He didn't know that he had to wait for his name to be called!"
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Andy Murray strolls out onto Rod Laver Arena, giving the crowd a wave as he is introduced. Kyrgios was held back by one of the stewards, though. He was in his own world, listening to his music. Seconds later, he is given the go-ahead and is met with a huge roar from an expectant crowd.
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The players are limbering up in the tunnels within the Rod Laver Arena. Murray is smiling, he's looking super relaxed. Behind him, Kyrgios has his headphones on and has a very stern look on his face. We're minutes away, folks.
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David Law
BBC Radio 5 live sports extra commentator
"All logic tells me that Andy Murray will be mentally too strong, too tight in his game. I watched their previous meeting in Toronto and it was the same on that occasion.
"It will be closer this time because I think Kyrgios is in a better place psychologically.
"The first set is vital. I don't think we will see him beat Murray from two sets down. He needs to get this place jumping from the off.
"Kyrgios is box office, he makes tennis enjoyable, he makes people who don't watch tennis watch tennis."
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David McQueen: Living in Sydney, expecting a ribbing if Murray loses! Fancy Andy in four though. Tactically and defensively too good at this stage.
Andrew Priestley: I'm not expecting to be very productive in work this morning while Murray vs Krygios is going on! A simple 3-setter please! #bbctennis
(We assume Andrew is supporting his namesake)
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But if Kyrgios is triumphant, the 19-year-old will become the first Australian man to reach the Australian Open semi-finals since Lleyton Hewitt in 2005.
And at 19 years and 280 days, he will also become the second youngest man in the Open Era to reach the last four in Melbourne. Mats Wilander - yep it's the Swede again - holds that record at 19 years and 111 days in 1983.
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If Murray is successful today, he will reach the semi-finals in Melbourne for the fifth time in his career. It'll be his 15th Grand Slam semi-final, overtaking Mats Wilander into 12th place on the list of most Grand Slam last four appearances.
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Piers Newbery
BBC Sport at Melbourne Park
"Murray has won his last 10 matches against home players at Grand Slams and has a 10-0 record against Australians, so that's all stacked up pretty well for him.
"He also has years of experience playing on Rod Laver Arena, while Kyrgios will be making his competitive debut there - prompting a few barbed words from commentators towards the schedulers over the last week.
"The general view appears to be that Murray's return game will eventually blunt the Australian's huge serve, while big-match fitness and experience also favours the Scot. Kyrgios was heard on the practice court earlier shouting, "Why am I so nervous?" It's anyone's guess what he will bring tonight."
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Murray has never lost at the Australian Open to a player ranked as low as world number 53 Kyrgios. If you were wondering, Juan Ignacio Chela - then ranked 51st - is the lowest-ranked player to defeat Murray in Melbourne. That was on Murray's Australian Open debut in 2006.
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We're expecting the players on court shortly, with BBC Radio 5 live sports extra already up and running. You can listen to commentary via the 'Live Coverage' tab at the top of the page.
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Nick Kyrgios hit the headlines with that stunning victory over Rafael Nadal at Wimbledon last year, but in the following round, he went down in four sets to Milos Raonic. This time around, the world number 53 feels better prepared.
"I think I'll be pulling up better than I did at Wimbledon," he says. "I know what to expect now, what I am going to be feeling, especially after a five-set match like that.
"It's massive confidence being 19 knowing that you can last matches like that. It's massive."
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Elaine McCallum: #AusOpen all the way from Scotland. Go Andy Murray.
Where are you planning on following Andy Murray's quest for a semi-final place from? Send us your tweets and photos to #bbctennis.
The tale of the tape
Murray v Kyrgios (08:15 GMT)
The players have met just once on tour, with Murray winning in straight sets in Toronto last summer. The Briton also won the set they played at the International Premier Tennis League (IPTL) exhibition in India two months ago.
"There were some things that I did in that match [in Toronto] which I believe will work on Tuesday," says Murray. "So I've learnt stuff from playing against him there and at the IPTL and watching him a bit, stuff that I feel I can use and exploit in his game."
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Piers Newbery
BBC Sport at Melbourne Park
"The atmosphere has been a bit flat around Melbourne Park so far today, possibly a collective hangover from Australia Day on Monday and possibly because of the autumnal 17C temperature and chilly breeze.
"There is little chance of things remaining calm as we head into the main event of the day, however. The match has been hyped from breakfast time this morning with the host broadcaster's 'Countdown To Kyrgios' clock on screen, and most of the spectators look like they decided not to change out of their Australia Day gear."
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At Wimbledon, Murray has a home crowd who will cheer his every shot and help carry him through the toughest moments.
Kyrgios will have that benefit of the home support but Murray is confident he'll be able to deal with the atmosphere.
"Obviously the crowd will be right behind him, understandably so," said the 27-year-old. "They're going to watch him play a lot of matches like this over the next 10, 15 years probably, and that's just something that I'll have to deal with in my way.
"I've played a lot of matches. I've played in the French Open against French players where the crowd can be very difficult. I've experienced it before, so hopefully I'll deal with it well."
Kyrgios's path to the last eight
Round one: Federico Delbonis (7-6 3-6 6-3 6-7 6-3)
Round two: Ivo Karlovic (7-6 6-4 5-7 6-4)
Round three: Malek Jaziri (6-3 7-6 6-1)
Round four: Andreas Seppi (5-7 4-6 6-3 7-6 8-6)
It's been harder work for Nick Kyrgios, who has had to come through two five-setters, including a thriller in the last round against Andreas Seppi, who was Roger Federer's conqueror.
But his success has made him the first home player for 10 years to reach the Australian Open men's quarter-finals. "When I saw I had finally won the match it was incredible. It was the best feeling I ever had," said Kyrgios. "It's crazy."
Get involved
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Craig Masters: Should Australia just hand the Open to Novak now or?... #ausopen #bbctennis
Mustehsan Beg: Vamos Andy! Let's do this #bbctennis #AusOpen
Daniel Eckersley: If any British sporting fans think Murray is/was arrogant, they're going to get a shock when they see Kyrgios. #bbctennis #AusOpen
Aussie fans may feel differently. Get in touch via #bbctennis on Twitter.
Murray's path to the last eight
Round one: Yuki Bhambri (6-3 6-4 7-6)
Round two: Marinko Matosevic (6-1 6-3 6-2)
Round three: Joao Sousa (6-1 6-1 7-5)
Round four: Grigor Dimitrov (6-4 6-7 6-3 7-5)
It was pretty much plain sailing for Murray on his way to the last eight, with only Grigor Dimitrov providing any real resistance.
The Scot was delighted with the way his body held up in the closing stages of that tussle, having struggled at times on his return from back surgery in 2014.
"My body allowed me to play that way for the whole duration of the match," said Murray. "I didn't feel tired. I felt fresh. My back felt good. I wasn't feeling stiff at all."
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Who is Nick Kyrgios? He's the chap who pulled off a between-the-legs winner against Rafael Nadal on Wimbledon's Centre Court last year.
And he's continued making a name from himself ever since.
"Smashed racquets, audible obscenities, conversations with the crowd, "cocky" on-court interviews, all among a blizzard of winners and aces - it has been impossible to take your eyes off him at Melbourne Park," writes BBC Sport's Piers Newbery.
Read more about him the 19-year-old from Canberra - and watch that between-the-legs winner - here.
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BBC Radio 5 live sports extra
Andy Murray and Nick Kyrgios headline the night session, with the players due on court at 08:15 GMT.
We've got a two-pronged attack of coverage for you this morning, with BBC Radio 5 live sports extra up and running with their build-up ahead of live commentary.
You can give that a listen by clicking the 'Live Coverage' tab at the top of this page and, er, hitting play.
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And that's where our focus moves, with Britain's Andy Murray bidding to win his first Australian Open title, after three final defeats.
Standing in his way is Nick Kyrgios, the 19-year-old phenomenon who has gripped the world of tennis and his home nation with his raw talent, wacky t-shirts and zig-zig designs carved into his hair.
Can the young pretender beat the two-time Grand Slam champion in the quarter-finals?
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So another seed bit the dust this morning, as Tomas Berdych completely outplayed Rafael Nadal, the 2009 Australian Open champion.
There was a bit of a wobble in the third set for Berdych, but who can blame him? The Czech was on the cusp of ending a 17-match losing streak which goes back to 2006.
But in the end, Berdych got across the line for a victory he thoroughly deserved.
His reward? A semi-final match against Britain's Andy Murray or Australian's rising star Nick Kyrgios, dubbed "Wild Thing" by the host broadcaster.
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Federer. Gone.
Nadal. Gone.
Murray. TBC