David Law
Commentator on BBC Radio 5 Sports Extra

We have increasingly seen Alcaraz change his postion on the return of serve from point to point. He doesn't just have one way of doing it.

More trouble here for Djokovic as Alcaraz gets to 30-30.

But the Serb nails the forehand to move to game point then a big serve gives him the hold.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Djokovic certainly enjoyed that zinger of a backhand winner in the fourth game.

Flicking his wrist through the air - as though he was cooling down his fingers - indicated how hot it came off the racquet.

Problem is there haven't been too many more of them. Instead the winners have been outweighed by errors as he struggles to keep a lid on Alcaraz's forehand.

Alcaraz ticks off another hold. Couple of forehand winners and a big 129mph serve. Job done.

The Spaniard still has that break of serve advantage.

Image source, Getty Images

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

There was just quite an angry exchance between Djokovic and his team there - maybe he isn't so calm!

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

We always see so many characters from Djokovic on court and you never know which one is going to come out.

Right now looks incredibly calm, he looks like he is going to play with calmness rather than anger.

Another missed dropshot from Alcaraz hands Djokovic a crucial hold.

Still early stages of this match but it already feels vital that the Serb stay in tough.

That glorious Djokovic shot is followed by a couple of not so glorious ones and Alcaraz takes the hold.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

When I was watching Alcaraz practise the other day, I'm sure he didn't miss a single drop-shot.

Casual, confident and clinical.

But the match court isn't the practice court, eh?

Image source, Getty Images

Vintage Djokovic! A stunning backhand rifled down the line and he smiles. A glorious shot after Alcaraz had got to game point.

Even the Spaniard purses his lips as if to say 'wow'.

Back to deuce.

How has he missed that?! Alcaraz shoves his forehand drop shot into the net. Well actually it hits the tape and drops back on his side of the court.

Deuce.

Woops. Alcaraz double faults and that could offer Djokovic a little glimmer of hope at 40-30.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Support is relatively split among the 25,000 fans on Ashe, I'd say.

Alcaraz's name was greeted by marginally more decibels before the match, helped by the vocal Latin contingent which always turns up in Nueva York.

Djokovic, as arguably the GOAT, commands respect and love wherever he goes though.

Djokovic is just stretching his neck out after Alcaraz moves to 30-0.

Boy has Djokovic had some problems at this tournament. It feels like he's had the trainer out in almost every match - lower back, neck, shoulder, blisters. You name it.

Alcaraz looked so relaxed during that game, despite missing the double break opportunity.

He was laughing and smiling after points. By contrast, Djokovic looked frustrated and tense.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Not for the first time over the past fortnight, Novak Djokovic serves his spots to get out of trouble in game three.

So clutch.

His opening shot is a weapon which he continues to rely on - especially in the key moments - as he heads towards retirement.

A big serve to the body gets Djokovic out of trouble and he follows up with a 124mph ace down the T.

A big forehand to the corner seals the game for the 24-time major champion.

After 16 minutes of this semi-final, Djokovic is on the board.

Image source, Getty Images

Alcaraz is piling the pressure on the Djokovic second serve. And the first serve come to think of it.

Djokovic can only return a crunching forehand wide and that brings up a break point for Alcaraz and the chance for the double break.

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

Maybe this is possibly the last real roll of the dice for Djokovic to get his 25th Grand Slam.

A very strong start from Alcaraz, who nails a couple of serves out wide to get to 40-15.

Djokovic misses the forehand, though, and that gives Alcaraz the hold and the consolidation of that break.