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.

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."

David McQueen:, external Living in Sydney, expecting a ribbing if Murray loses! Fancy Andy in four though. Tactically and defensively too good at this stage.

Andrew Priestley:, external 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)

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.

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.

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."

Image source, 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.

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.

Image source, 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."

Image source, ElaineMcCallum/Twitter

Elaine McCallum:, external #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 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."

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."

Image source, Getty Images

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."

Image source, Getty Images

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."

Craig Masters:, external Should Australia just hand the Open to Novak now or?... #ausopen #bbctennis

Mustehsan Beg:, external Vamos Andy! Let's do this #bbctennis #AusOpen

Daniel Eckersley:, external 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, external on Twitter.

Image source, Reuters

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."

Image source, EPA

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.

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.

Image source, Getty Images

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?

Image source, Getty Images

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.