Djokovic should really win this point, Federer stretched all over the show... and he spears a backhand long!

Deuce.

A yell from Djokovic as he flaps a backhand into the net, Federer charging forwards like he's a puppy chasing after a ball.

That's brilliant returning from Djokovic, pushing the ball so deep onto the baseline, and Federer picks a terrible time to double fault to go 15-30 down.

Brilliant reactions at the net from Federer get him on par but that's loose and it's break point to Djokovic...

Novak Djokovic is so, so dominant on serve.

A blistering winner is the only look-in Roger Federer gets, Djokovic cracking down aces and service winners for fun, and the Serb holds to 15 with such ease.

Roger Federer belts down two aces to get his service game under way, but he's outpowered in a rally and nets his backhand for 30-15.

He charges the net, serve and volleying his way to game point, and a serve out wide gets him out of a tight spot.

Image source, AFP

Smash.

Djokovic races to a love hold, and all the pressure is back on Federer.

Djokovic spreads his arms and gestures to his box as he plonks a backhand long in response to Federer's second serve.

Djokovic is on the move as he hooks a forehand cross-court... ooh, and he's just, just, pulled it wide!

That's a good hold for Federer.

Big serving from Federer and this time Djokovic spoons his return long.

Hiya, deuce.

Wallop.

Ace.

30-40.

Federer slaps his hand against the bottom of his racquet as he plants a forehand into the net, before he rips a first serve through Djokovic to get on the board.

Federer's trying to keep the points short but that's an outrageous passing shot from Djokovic, his backhand flying into the corner, and that's another sublime winner, this time on the forehand, from Djokovic.

Two break points for Djokovic...

Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Live Sports Extra

Is winning three sets an insurmountable hurdle for Federer now? What is he thinking?

We didn't see his usual explosive movement in that first set especially when hitting on the forehand side, but you can't expect that having played two five-set matches.

He's not going to have the same spring in his step.

Image source, Getty Images

After a competitive first set this all feels rather... flat.

Novak Djokovic races to a 40-0 lead in front of a near-silent crowd, Roger Federer's backhand sending back error after error, before Djokovic skews his own forehand wide.

That's an easy hold for the Serb.

Roger Federer is back.

It'll be Novak Djokovic who'll serve to get this second set under way.

Jonathan Jurejko
BBC Sport at Melbourne Park

No major celebrations from Djokovic as he closed in on, then won, that first set.

A raised right arm and a stern side-eye to his box - and those vocal supporters sat a few rows behind them - greets the set point.

And then he raises the opposite fist towards them as he walks back to his chair with a quick glance backwards.

Roger Federer has taken a medical timeout, while Novak Djokovic has been given some pills for what I think is a headache.

They've stopped playing YMCA, mercifully.

The doctor is now having a word with Novak Djokovic.

Brilliantly, he can't hear what the Serb is saying because the PA is playing YMCA at an ear-bleedingly loud level.

Now then, the doctor is out for Federer...

He's heading off court.

And a belting return of serve hands Novak Djokovic the first set!

From 4-1 down, that is an almighty comeback from the defending champion.

Image source, AFP

Russell Fuller
BBC tennis correspondent at Melbourne Park

Some emotion for the first time from Djokovic as he clenches his fist. Suddenly he looks in command of the court.

That's disgustingly good from Djokovic!

He somehow manages to swirl a winner around the net post and the ball turns and bounces in, handing him five set points.

Thwack. Ace.