Excellent placement from Murray as he sends Kokkinakis running to one side of the court, then the other.

But the Australian gets some payback on the next point with another huge forehand winner to bring up deuce again.

This looks to have slipped out of Couacaud's reach now.

Djokovic earns two break points on the qualifier's serve, Couacaud saves the first with an ace, but hands the second to Djokovic.

The Serb lets out an almighty roar and he needs just two more games for a place in the third round.

Murray saves the first break point as Kokkinakis finds the net and a barrage of slices sees off the second.

Deuce.

Make that 15-40 down.

Murray struggles to control a smart Kokkinakis forehand as it falls earlier than expected.

This set could be over in no time.

No end to the funk in sight currently as Murray goes 15-30 down on his serve.

Jonathan Jurejko
BBC Sport at Melbourne Park

The celebrations were almost muted when Kokkinakis held for 4-2 - because the crowd couldn't believe how long that forehand was from Murray.

It was nearer Row A than the baseline.

Murray is in a funk and needs something - anything - to get him going.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Sports Extra

Things are not exactly going Murray's way. He can't get any rhythm going and Kokkinakis is moving quickly.

We've talked about the cooler conditions but this is a classic case of Andy just mistiming it and his footwork wasn't quite there.

Couacaud makes use of Djokovic's lost focus and earns himself a first break point of the day.

He fails to keep in Djokovic's serve, however, but then saves game point. He can't the next, and Djokovic holds a tough game.

The hecklers, dressed as 'Where's Wally?', have been given a talking to.

Kokkinakis cools the nerves with a third ace of the match to open up his service game.

Murray gets increasingly frustrated with himself as his backhand sails long to bring up 40-0.

He massively overcooks a forehand next and hangs his head after Kokkinakis holds. Reset needed on Margaret Court.

Jonathan Jurejko
BBC Sport at Melbourne Park

Murray looked worryingly sluggish at times in that game, particularly when he dumped that backhand into the net for the first two break points.

Those legs could be heavier than a pair of kettlebells.

And he's already chuntering at his box which is never a good sign.

Russell Fuller
Tennis correspondent at Melbourne Park

Andy Murray's got himself into pretty good shape, and I think he is clearly in the best shape he has been in since he was world number one and pretty much winning everything in sight in 2016.

I don't think this will be a really long match with long rallies, which will perhaps be in his favour and we shouldn't forget that Thanasi Kokkinakis, even though he is nine years younger, has had all sorts of injury problems over the years.

He didn't have such a gruelling first round match and he had to hang around yesterday afternoon until he could finish the last few points of the match after the rain.

I think if Murray is able to play with relative freedom he would definitely be the favourite for the match.

Here's what our tennis correspondent Russell Fuller thought would be needed from Murray before this match began.

It's a lengthy rally, but Murray sends the ball into the net to bring it to an end.

This is so closely fought so far, sense it could be a long one. Glad I brought a sandwich to my desk!

There's one man in the crowd who is heckling Djokovic relentlessly and, as probably intended, it's getting under the Serb's skin. "What are you going to do about it?" he asks the umpire. Djokovic doesn't get the answer he wants.

Could it be having an effect on him? He loses a 40-15 lead and then the first advantage from deuce.

He is rattled....back to deuce.

Another one for Kokkinakis! He moves Murray forward and back then slaps the ball past him in the corner.

Murray is predictably displeased.

Eek, Andy Murray's forehand only just lands on the line and Thanasi Kokkinakis takes a good look at it. It's eloctronic line calling so there's nothing the Australian can do about it.

He responds on the next point with a lovely backhand down the line to bring up deuce.

Image source, Getty Images

Super serving - second break point saved.

Relax everyone.

Ok, Murray is all action. He comes to the net to bat down a winner and save the first break point.

Oh DEAR.

Murray's backhand finds the net and Kokkinakis finds two break points.

The crowd is raucous.

Jonathan Jurejko
BBC Sport at Melbourne Park

The over-exuberant Aussies waving their flag between points are given a telling off by chair umpire Eva Asderaki-Moore, but it doesn't put them off celebrating when their man holds.

This place is ready to blow. They just need Kokkinakis to light the fuse.