Excellent service game from Alex de Minaur.

Some heavy serves and, encouragingly for the Australian, he also manages to get the better of Jannik Sinner in a couple of rallies.

Sinner is going to have to serve it out.

David Law
Commentator on BBC Radio 5 Live and BBC Sounds

The sheer velocity of the cross-court arrow that is being fired across there by Jannik Sinner is just too much for De Minaur.

Jannik Sinner hasn't given Alex de Minaur a sniff of a break so far.

There are a couple of nice rallies but Sinner is in control and, even on the occasions where De Minaur thinks he might have got the upper hand, the top seed quickly finds an answer.

Sinner is one game away from taking the first set.

"Come on!" shouts Alex de Minaur after watching a Jannik Sinner forehand go long.

That puts the Australian 30-15 up, a big first serve makes it 40-15 and another clinches a comfortable hold.

De Minaur needed that.

Image source, Getty Images

Alex de Minaur senses an opportunity to break straight back as he goes up 0-30 after a 23-shot rally ends with Jannik Sinner sending a slice long.

Sinner has other ideas, though, and some big serving helps him race through the next four points.

David Law
Commentator on BBC Radio 5 Live and BBC Sounds

Alex de Minaur will try every little thing in his arsenal before this is over and whether it's enough, who knows. He needs to find some way to hurt Jannik Sinner here.

A shake of the head from Alex de Minaur as he fails to finish off a point he had bossed, putting a volley into the net.

That makes it 30-15 and a pair of forehands into the net later and Jannik Sinner earns the first break point of the match.

De Minaur even offers him a second serve but Sinner puts his return into the net.

The Italian keeps coming, though, earns another break point and comes out on top in a lengthy rally when De Minaur pulls his backhand wide.

Image source, Reuters

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

When Jannik Sinner is moving laterally it looks like he's going down the mountain on skis, the balance is superb.

Jonathan Jurejko
BBC Sport in Melbourne

Hmmm, it's not quite the raucous atmosphere which we thought it might be.

Clearly the Aussies did not get fired up at the bar during that extra 45-minute wait.

Quite muted for now. That might change as more pile in after the third game and if the Demon manages to forge a lead.

Annabel Croft
Former British number one on BBC Radio 5 Live and BBC Sounds

Alex de Minaur has just got to take as much time as he possibly can away from Jannik Sinner because that's what Sinner does to everybody else, but it's still not going to be easy.

No sign of the issues that hampered Jannik Sinner in the last round so far.

He's striking the ball cleanly and has Alex de Minaur scampering around the court before showing good touch at the net to finish the point.

An ace, Sinner's second of the game, wraps it up.

Image source, Getty Images

Jonathan Jurejko
BBC Sport in Melbourne

There is a brief pause before Sinner's service game as someone in the crowd behind De Minaur seems to take a tumble.

The gasps when it happens alert De Minaur, who looks concerned as the person is helped by those around.

A thumbs up from someone else on that row indicates we're good to go.

Annabel Croft
Former British number one on BBC Radio 5 Live and BBC Sounds

It's a really interesting forehand because it has a slight curve on it when [Sinner] strikes it, it's a natural strike that creates this sort of curve with the ball with the spin, it travels away from the opponent, and it comes with a bag of concrete attached to it.

Big cheers from the fans in Melbourne as Alex de Minaur wins the first point on his serve after wrong-footing Jannik Sinner.

The Australian gives Sinner a couple of looks at his second serve but it doesn't prove costly this time as the top seed sends a forehand long and De Minaur holds.

Image source, Getty Images

Annabel Croft
Former British number one on BBC Radio 5 Live and BBC Sounds

If anyone has an amazing attitude it's Alex de Minaur, somebody who has maximised everything he brings to a tennis court. You never see his head drop, he gives a thousand percent every single ball that gets played out there.

He's probably someone who likes a challenge and is up for it and is looking for solutions to the problem that's in front of him.

Strong start from Jannik Sinner.

The defending champion runs around the ball to whip a forehand winner down the line to go to 40-15 before Alex de Minaur's return goes long.

Comfortable hold to begin the match for Sinner.

Annabel Croft
Former British number one on BBC Radio 5 Live and BBC Sounds

I was looking at his expression when he came out on to court and he looked very deadpan, he hides his emotions a lot, it's very, very difficult to get into the head psychologically of Jannik Sinner, he gives nothing away.

David Law
Commentator on BBC Radio 5 Live and BBC Sounds

De Minaur hasn't won a set in the last seven meetings between these two, that in itself is glaring isn't it and frankly the sets haven't even been close either.

Image source, Getty Images

If Jannik Sinner needed a pick-me-up after struggling his way through his fourth-round match, a quick look at his record against Alex de Minaur might well have done the trick.

The Italian has won all nine meetings - and claimed another victory by walkover - between the pair, only dropping one set of the 21 they've played.

Jonathan Jurejko
BBC Sport in Melbourne

Shaking in his chair and more pale than usual, Jannik Sinner looked a real mess during his win over Holger Rune on Monday.

Morning after the Christmas party vibes. Sinner certainly wouldn't have been on the lash.

Rumours have been swirling around Melbourne all day about his physical condition, but he looks fresh enough as he wanders in the underbelly of Rod Laver Arena and kicks a ball with his fitness trainer in a warm up.

Proof will be in the pudding. De Minaur, a Duracell Bunny of a player, is bound to be testing out his condition.