Live Commentary: Denis Istomin vs. Novak Djokovic - as it happened

Good morning tennis fans. Slightly behind schedule we have reigning champ Novak Djokovic on Rod Laver Arena, taking on Denis Istomin.

Istomin will serve once the players warm up. The reason for the delay to this game was that we had a lengthy match between Ana Ivanovic and Sam Stosur to begin the evening session. The Serbian eventually took it in three, and it could well be a Serb double should Djokovic get through also.

Djokovic is unbeaten in competitive tennis since he lost the US Open final to Rafael Nadal. It's currently 26 matches - a daunting prospect for Istomin. Of course, Istomin has the ability to push Djokovic - a little, at least. He very much struggles with inconsistency so I'd be surprised if he managed a set here.

Here we go then... It's a very good start from Istomin who is immediately 40-0 up.

Djokovic gets on the board with a fine forehand winner and then an absolutely unbelievable backhand pass gets another back. What a shot so early in the game!

Too little, too late in the game from Djokovic and Istomin holds for a solid start to his match. How can Djokovic respond with his first service game?

Djokovic is really starting to fire. He spins a bouncing second serve, before dominating a rally to finish with a powerful forehand for 30-15. He crafted that so well.

The Serb holds comfortably with another forehand winner - his third of the match so far. Both men have started well with their serve.

Djokovic takes advantage of some nerves from Istomin and has two break points early in the first...

BREAK! It's a good rally, but you fancy Novak every time in one of those. Istomin tries to force the issue but puts a backhand wide to undo all his early good work. Advantage Djokovic.

It's all too easy for the favourite at the moment. It's a comfortable hold to love for the Serb, with no resistance at all from Istomin. He needs to pick up his game quickly of this one will be out of sight.

A good response though from Istomin. He manages to return to the level of his opening service game to breeze through one of his own. This first set is not hanging about.

Too good from Djokovic. At 15-0 he decides to come to the net, and finishes the point with a big smash after guiding a forehand right into the corner.

Then follows that up with a drop volley that Boris Becker himself would be proud of. That shot must have come about from their new partnership.

Another love game for the champion, who really showed all the facets to his play in that one game. Lovely stuff.

A good response to losing the first point there from Istomin, who drives a good serve down the line before finishing up with an overhead volley.

The crowd sound like they are watching fireworks at the moment as Djokovic clips the line with a forehand from out wide.

Istomin nets at 40-30, which means deuce. His level is going up and down all over the place at the moment, as he then produces a fine serve that's returned into the net for advantage. Then there's an unforced error from the Serb to gift the game to Istomin. He's clinging on at the moment, the Uzbek.

New balls, same Djokovic, as the reigning champ plays a nice one-two with a backhand winner.

Good play from Istomin to bring it to 15-30 as Djokovic goes long with a forehand. There's a slight look-in here.

And it takes the very best of Djokovic to bring it level. Both men were whacking it from the baseline and, once again, it was Istomin who missed out with a backhand into the tramlines.

The Serb then wraps up his serve, but it was the first one in which he was troubled. Istomin must hold here or he goes a set down. I fancy Djokovic to come out flying in this game.

What a brilliant winner under pressure from Istomin! Djokovic is on top of a point but his opponent spins a winner right around the post and on to the line to level it at 30-30. It rightly gets applause from Novak. However, the following point it's set point to the Serb...

SET! Sure enough, Djoko does not need two chances and he wraps up the set at the first time of asking. He was more than good enough then, but there's definitely more still in him.

Istomin is getting some treatment on his leg and we have a break in play for a medical timeout. An update: Fabio Fognini has got through against Sam Querrey - he will play the winner here.

He's not moving comfortably out there, and being run ragged in a rally by Djkovic is not going to help his cause! It's 15-15 on Novak's serve to start the second.

Djokovic is almost playing with Istomin now! He's going from one side to the other and the Uzbek finally ends up on the floor after some heroic defence.

Despite Istomin's struggles, it wasn't the easiest of holds for Djokovic, but a hold is a hold and he's off and running in the set.

Istomin is 30-15 up here and he's holding up ok. It was a poor backhand from Djokovic, with Istomin then following up with his second ace of the match.

Really well played there from Istomin, who holds comfortably. He's not been able to have a say against the Djokovic serve as yet so will he be able to in this game?

After a couple of moments to regroup, Djokovic fires a wonderful backhand winner but then nets another to give Istomin something of a chance in the game. Can he capitalise?

A really goof chance for Istomin to get break point, but instead he fires his backhand long and it's 40-30.

Another tough hold, but Djokovic manages it despite being well below his best in the game. Istomin will be encouraged by his response since the injury, but it's vital he holds serve here.

That said, it's 0-30... Huge point coming up.

BREAK! There it is. It was important to hold, but instead he's been broken to love. He's had no change from the Djokovic serve so far and if that continues he'll be two sets down.

Now 15-30 - this is the third time Istomin has had this situation. He's blown the other two, what now?

He blew it again. A really poor forehand from the baseline under little pressure goes long, which Djokovic follows up with a brilliant winner.

It's a commanding lead for Djokovic now, although it is still just the one break. His response when in trouble on serve has been impressive today. Istomin has been his typical inconsistent self, which just isn't good enough against the world's best.

Djokovic reads a volley well, but can't react quickly enough to direct back over the net. From 0-15 Istomin moves up to 30-15, then hits a good serve that's returned into the net. Good so far.

But you cannot keep Nole down. He crafts a point really well before finishing off with a powerful inside-out forehand winner.

Djokovic nets a return and Istomin has another game on the board. A break some time soon would be very handy for him!

Lovely point. Istomin defends really well before clipping the top of the net with an attempted pass. It sits nicely for Djokovic to put into the open space, and he then finishes the game off for a comfortable hold. This one is only heading one way.

Djokovic plays a bit of 'Who Wants To Be A Millionaire', asking the audience if he should challenge. They think he does, so he does. He's wrong. We're at 30-30.

Istomin passes the first test: the hold. Now comes the much, much tougher one of breaking the reigning champion.

It's not looking likely as Istomin goes long for 30-0.

SET! Too good Djokovic. He sends Istomin the wrong way for 40-0 and then wraps up the set on his first set point with a sweeping forehand into the corner. The Serbian double is very much on, barring one of the most surprising comebacks tennis will have ever seen.

A really strong hold from Istomin to start the final set. He has just five winners compared to Novak's 23 - Nole's pace on the baseline is the big difference.

Djokovic goes for another one there at 30-15 up, but just sees his forehand skid past the baseline.

Djokovic follows up with an easy hold of his own. So far the set is being played at a canter, with little challenge to either's serve. That will probably change here..

Brilliant from Djokovic, who guides a backhand winner into the corner to set up the first break point at 30-40.

Clean winner from Istomin, who latches on to a quick return with a shot down the line for deuce.

BREAK! It's a break in Istomin's second serve once again for Novak, and this is the beginning of the end for the Uzbek. Djokovic can cruise this one home now.

Istomin is doing his very best to hang on in points, but Djokovic has him running all over the court. After a long rally, a drop shot is just too good.

A late rally from Istomin here as he brings it to within a point of deuce.

Nope. He nets an attempted winner on the forehand and the world number two consolidates his break to move just three games away from victory.

Boom! Best winner of the afternoon for Istomin, who on the run slashes a forehand back across court and past Djokovic, who wasn't even far away from it. Now he's 40-0 up with another booming winner off the backhand.

He's bettered it! Initially an ace call is overruled by the umpire - even to Djokovic's disappointment. But no matter, after a fine return form the Serb Istomin slashes a backhand right on to the edge of the line for a hold to love. The crowd are on their feet and he's lapping it up. He won't go without a fight, which is good to see.

Djokovic just cannot put him away at the moment. This time Djokovic comes into the net and puts a volley long.

Much better from Djokovic, who levels it up before smashing an ace down the T for 30-15.

He's hitting winners left and right now, the Serb, and takes a 4-2 lead with a sweeping forehand on to the line. The momentum has shifted back.

Istomin is staying in rallies slightly better in this set, and Djokovic goes wide to make it 30-0, before being forced long on the backhand. Game point.

Another hold for Istomin and he won't give up the fight easily. It hasn't been the most competitive of contests, but he's played his part in the third.

A hold to love for Djokovic ought to finally knock the wind out of Istomin's sails, though. He has to hold to stay in the match.

Brilliant serving, however. He goes up 40-0 with ace number five...

"Over to you, Novak," says Istomin. To himself. The Serb is yet to drop a service game and having been in far higher pressure situations than this, he should take this comfortably.

Having said that, Istomin is 0-30 up. He was on the floor after a good stretching backhand that Novak put wide at the net.

At 30-30 Djokovic makes his first double fault to set up Istomin's first break point of the match...

BREAK! Well I never! As if from nowhere Istomin produces a break and we're level in the set. Djokovic might require a breaker to win this.

Both men are finding the corners and at 30-0 Djokovic finds an important winner.

Djokovic stepping it up at just the right time. From 30-0 he has break point at 30-40...

That one is saved, but he sets up a second with a forehand into the open space he had created.

BREAK! Huge roar from the champion as he manages to break back! He's delighted with that and here comes his second chance to serve out the match. I said it before, but I definitely don't see him losing this time...

Djokovic is 30-0 up following a backhand into the net from his opponent. Not long now.

Despite a stunning return a moment ago, it's two match points Djokovic...

Not yet! Djokovic comes to the net and is beaten by a backhand pass down the line. One match point remains.

Djokovic is into the last 16 without dropping a set. This third set was his toughest so far and he was by no means flawless tonight. But he still had more than enough to get past Istomin. Next up is 15th seed Fabio Fognini.

Djokovic, speaking to Eurosport after the game:

"It was never going to be easy, Denis is a quality opponent. He almost came back into the match and it was very close in the third, but I did not want to drop the set and have to play a fourth.

"Me and my team are my biggest critics. I have to be pleased with the way I've played so far and I get better and better, that's the way I play [in tournaments].

"It's been great [working with Becker]. We have a great understanding with each other and I can't wait to get Boris in the court and get going with him.

"Fabio is a friend of mine. We grew up together and are the same generation. We have played each other several times on different surfaces. He is top 15 in the world and there are no easy matches."

Thanks for joining up for this match to end day five of the Australian Open. We will have more commentaries for day six, so be sure to stick with us then. Goodbye for now.