Hey, Mark, come on. You know the drill. Get to work, open BBC Sport live text, hide your screen from your boss until further notice

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Djokovic was in ruthless form the last time he met Nishikori, losing only two games on the way to victory in the opening match of the ATP World Tour Finals in London in November.

But his Japanese opponent came out on top in their last Grand Slam meeting - in the US Open in 2014 - where he went all the way to final before losing to Marin Cilic.

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There's some men's doubles happening on court two in Melbourne.

As I type, it's one set all between Jamie Murray/Bruno Soares and Raven Klaasen/Rajeev Ram.

A semi-final place is up for grabs.

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Straw hat? Check. Inflatable kangaroo? Check. Posing in front of a meat-filled barbie? Check.

Poland's Agnieszka Radwanska - fresh from her progression to the women's semi-finals - got into the spirit of Australia Day and had a go on the old BBQ outside the Rod Laver Arena. 

We do love a good national stereotype. 

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He may be world number one, but Novak Djokovic endured a difficult route into his 27th consecutive Grand Slam quarter-final. 

It took the Serb over four hours (and 100 unforced errors) to get past Gilles Simon of France in five sets.

Kei Nishikori, meanwhile, casually dispatched Jo-Wilfried Tsonga in straight sets in the last 16. 

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It may still be dark outside in the UK, but the day is almost done in Melbourne.

Here's what you might have missed:

Serena Williams didn't hang about in her bid to reach the semi-finals. The American top seed saw off Maria Sharapova for the 18th time in a row, winning 6-4 6-1.

Next up for Williams is Agnieszka Radwanska of Poland, who beat Carla Suarez Navarro 6-1 6-3.

And in the men's singles, 17-time major winner Roger Federer looked in brilliant form as he overcame Tomas Berdych 7-6 (7-4) 6-2 6-4.

Federer will now face the winner of Djokovic v Nishikori. 

Fancy some Australian Open in your ears? 

Click on the live coverage tab on the top of this page and have a listen to Tennis Breakfast, courtesy of BBC Radio 5 live Sports Extra. 

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We've intravenously administered coffee into our veins, shoved some brekkie in our belly and now we're limbering up for the last of Tuesday's matches in Melbourne. 

World number one Novak Djokovic against seventh seed Kei Nishikori of Japan is due to start at around 08:00 GMT.

Federer disappears which means we're disappearing too, but only for a short while. There'll be more live coverage from us at 08:00 GMT for Novak Djokovic's ding-dong with Kei Nishikori. It promises to be a great match, Federer said so. 

To catch up with what's been happening at the Australian Open today, click here. If you're already clued up, take a breather and join us again in a couple of hours. 

Federer has yet to lose an Australian Open quarter-final. Incredible. That victory over Berydch was his 80th in the tournament and means he reaches his 39th Grand Slam semi-final. Just incredible. 

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"It's going to be more running in the next match, regardless if it's Nishikori or Djokovic, so that's going to be interesting," says Federer of his potential semi-final opponents. 

Asked whether he'll watch the semi-final, which will begin at about 08:00 GMT, Federer says: "I think I'll find some time for that. As a fan it'll be a great match so I think I should watch it and as an opponent, yeah, I'll watch it."

"I'm very, very happy," says Federer. 

"Tomas has caused me a lot of problems over the years, but it's been a pleasure playing against him, he's the type of player who makes you better. 

"I thought I played a good match. I was aggressive, had variety in there, it was good conditions to play in."

Magical. Brutal hitting from both players from the back of the court, but it's Federer who steals the show, a stunning backhand winner for a fourth break point. 

A momentum-changing forehand, Berdych stunned, netting, and the Swiss will serve for the match. 

And here we go. Three break points Federer and the decibels inside the arena rise. The Czech saves one, saves two... the Berdych supporters (of which there aren't many) find their voice... 

One more chance... Berdych rolls the dice, a forehand into the corner which is called out, but HawkEye says it was in by 0.000001mm. The point will be played again and the Czech responds with an ace. 

Three break points saved. Gutsy from Berdych. On the next point, the sixth seed is aggressive, stepping in and forcing Federer to net. 

Berdych gambling, going for the big winners, and at advantage it doesn't pay off, a forehand going long. 

Advantage. Deuce. Brilliant returning from Federer. We go on. 

Kerpow! Sublime serving from Federer, competing a hold to love in under a minute. The Swiss serving with the accuracy of his country's clocks. 

One  beaut of a shot from Federer, his backhand a thing of beauty, to level at 15-15. The quality of the shot-making suggests he might be preparing to pounce, but Berdych proceeds to rattle through the points to hold to 15. 

Blimey. Two break points Berdych, but Federer saves both thanks to accurate serving when he needs it the most. A forehand winner, then a backhand crosscourt screamer, from the brink to parity, the crowd can't help but admire, Federer can't help but clench his fist.