Much, much better from Jannik Sinner.

Ben Shelton is able to return the Italian's serves but Sinner is quick to advance and a couple of quick serve-volley combos help him on his way to a comfortable love hold.

Jannik Sinner makes a move to the net, but he doesn't do enough with the volley and Ben Shelton takes advantage with a cross-court passing winner.

And then a big second serve sees him through. He backs up the break.

Image source, Getty Images

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

Ben Shelton needs to be able to connect and coordinate his first serves. He is going to need some firepower with his first strikes.

Jannik Sinner is picking up some of them quite well but he is just pulling some of them wide.

Despite being in just his second Grand Slam semi-final, it doesn't seem like Ben Shelton feels like he is under too much pressure. The American does a couple of keep-ups with the ball before serving!

We go to deuce as Jannik Sinner finds the net on his first break point.

Shelton then has two chances to get the hold over the line, but twice he misses and we're back at deuce.

Three misses from Ben Shelton open up the door for Jannik Sinner to break back immediately.

Image source, Getty Images

Andy Murray on whether he would like to continue coaching Novak Djokovic: "It has been a steep learning curve for me as well. There's a lot of things that you obviously know as a player, but things are different when you are coaching. There is a lot more that you need to help with, in terms of communication with the team. You aren't just thinking about yourself, like you are when you're a player.

"I've certainly learned a lot but there's still a lot more for me to learn, that's for sure.

"I said I wasn't going to talk about that [the future]. I was clear about that. Me and Novak agreed that after the tournament we would speak - and we will do that."

What about that?!

Jannik Sinner looks like he's taken out Ben Shelton with a forehand into the corner, but the American recovers and plays a stunning pass down the line.

The crowd loved that and Shelton has an early break against the defending champion.

Ah! A poor miss from Ben Shelton, who tries to switch up play with a backhand slice but the ball falls short at the net.

He's got another crack, though.

An early opening for Ben Shelton, who is handed a 0-30 lead as Jannik Sinner fires long.

The American hangs his head back in frustration on the next point after pushing into the net.

But here we go! Sinner nets and hands Shelton two break points. What a start this would be for the world number 20.

Here we go then. A place in the Australian Open final is at stake.

Defending champion Jannik Sinner serves first to get us started in this semi-final...

Image source, Getty Images

After his quarter-final win over Lorenzo Sonego, Ben Shelton criticised "negative" and "disrespectful" on-court interviews with players at the Australian Open.

The on-court interviewer suggested no-one would be cheering for the 22-year-old in his next match.

"There are some comments that have been made to me in post-match interviews by a couple of different guys," said the world number 20.

"Today on the court, 'hey, Ben, how does it feel that no matter who you play in your next match, no-one is going to be cheering for you?'.

"I mean, [it] may be true, but I just don't think the comment is respectful from a guy I've never met before in my life."

Image source, Getty Images

Andy Murray on watching Novak Djokovic's injury end his chances of a 25th Grand Slam title from the sidelines: "It's hard. When you get to that stage of the tournament, you feel like you are getting very close to something very special. It's unfortunate when your body isn't responding in the way that you would like. In Novak's case, there is always hope with him because of how great he is as a player. He has found ways out of difficult situations before, but it just wasn't to be this time."

Here they come...

Ben Shelton's got his hood up, headphones on and he shows the crowd a small smile and a wave.

Jannik Sinner, in an all-white outfit, looks calm and confident as he gives a relaxed nod to the fans on Rod Laver Arena.

Image source, Getty Images

This will be Ben Shelton's second Grand Slam semi-final, while it's a fifth for Jannik Sinner.

Shelton lost in straight sets in the last four of the 2023 US Open to eventual champion Novak Djokovic.

Image source, Getty Images

Jannik Sinner and Ben Shelton have played each other five times.

Shelton won their first meeting in Shanghai in 2023. But Sinner has since won each of the last four, and has taken nine straight sets off the American.

Image source, Getty Images

There were big concerns over Jannik Sinner's physical state before his quarter-final against Alex de Minaur on Wednesday.

The defending champion had struggled with illness in his previous match against Denmark's Holger Rune.

But Sinner looked sharp with a 6-3 6-2 6-1 thrashing over eighth seed De Minaur.

"I feel like the illness has gone away now. I was feeling much, much better," the world number one said.

"When you are young you recover very fast - so it's a bit different."

Right, let's turn our attention to our second semi-final.

Can the big-serving Ben Shelton put a stop to Jannik Sinner's sizzling 19-match unbeaten run in Melbourne?

Hit the thumbs! Up for Sinner, down for Shelton.

Russell Fuller
Tennis correspondent on BBC Radio 5 Sports Extra and BBC Sounds

It doesn't happen often with Novak Djokovic.

He had this reputation of pulling out of matches early in his career. He had breathing difficulties during those days, so during his late teens and early 20s he had a reputation for doing it.

Andy Roddick used to try to humiliate him and laugh at him in public about the number of retirements. But, since he retired from the Australian Open quarter-final against Roddick in 2009, he has only retired from two other matches at Grand Slams.

We just didn't know what to expect today because we have seen him manage pain remarkably well in the past. He has been able to gradually improve and play through the pain, but this injury was obviously just a little bit too severe.

As always, we want to hear from you!

Do you think we'll see Novak Djokovic at Melbourne Park again? Reckon he's got enough left in the tank to win a record 25th Grand Slam title?

And who are you backing in today's other semi-final - Jannik Sinner or Ben Shelton?

Let us know all your Australian Open thoughts using the details above.

Image source, Getty Images

In other news, there's been plenty of British success today.

Britain's Alfie Hewett and Gordon Reid won a sixth successive Australian Open wheelchair doubles title, while Andy Lapthorne triumphed in the quad doubles final.

Top seeds Hewett and Reid defeated Spain's Daniel Caverzaschi and Frenchman Stephane Houdet 6-2 6-4 to claim their 22nd Grand Slam title as a partnership.

Lapthorne and Dutchman Sam Schroder won the quad wheelchair doubles with a 6-1 6-4 victory against the top seeds, Niels Vink of the Netherlands and Israel's Guy Sasson.

Not a bad day's work for Hewett, Reid and Lapthorne!

Read more here.