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A much more confident service game from Sinner and he gratefully takes the hold to 15.

Write him off at your peril.

Marion Bartoli
Former Wimbledon champion on BBC Radio 5 Live

Alcaraz is just able to showcase so much variety.

Sinner is facing the problem of returning first serves. He cannot get a grip of them at all. He needs to keep holding his serve if he wants a chance in this match.

Too good from Alcaraz. He has Sinner zipping back and forth across the baseline but it's too rapid a forehand in the end and the Italian can't get there.

A change of pace on the next point has the crowd ooh-ing and aah-ing and that wraps up the hold to 15 for the Spaniard.

Marion Bartoli
Former Wimbledon champion on BBC Radio 5 Live

Image source, Getty Images

It is bizarre the tennis we have seen in set one and set three. It is so uncharacteristic from Sinner to get beat like that on this court.

I am not sure the exact reasons behind it - is it his injury or just a lack of energy? Or is it that Alcaraz is just unplayable?

Sinner is showing so much frustration towards his camp.

Sinner takes the hold after a 12-minute opening game.

Two break points saved and he's on the board in set four. But my, my it was tough going.

WOW.

A couple of brilliant volleys. Sinner puts it out wide and Alcaraz somehow flicks his wrist round to make the return but Sinner keeps it in play with a return at full stretch. Glorious tennis and Sinner waves to the crowd for more noise.

Second break point saved.

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

We have seen so many mixed shots from Alcaraz. He produced the fake drop shot and then forces the racket head forwards. It means Sinner is playing catch up in the rally. Clever play from Alcaraz.

There is amazing respect between them - but I have seen some fists from Sinner right into the face of Alcaraz. There is definitely some needle there.

Sinner is getting really wound up here. He is like a volcano about to explode.

Sinner double faults and that gifts Alcaraz a second break point.

The Italian has been under serious pressure on serve for much of the evening.

Goodness me. Sinner's forehand is just inside the line and Alcaraz chases it down, almost doing the splits as his racquet finds the ball but can only send it sailing out of court. Break point saved.

Sinner wins the next point but Alcaraz puts the game back to deuce with a stunning drop shot.

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Alcaraz picks up where he left off and he's already got a break point in the opening game of set four.

Brilliant movement and shot selection from the Spaniard.

Just 29 minutes that set took. So it's no wonder Alcaraz is up and out of his chair early - raring and ready to go for set four.

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

An angry forehand from Sinner. Venom on that shot. He is taking it all out on the cross-court forehand.

Sinner can turn this around but he will have to do it quickly.

Alcaraz moves to within one set of the US Open crown.

Fist pumps from the chair from Alcaraz but he looks like he's trying not to get too carried away.

As we keep saying, this could still go anywhere.

Two first serves and a crunching forehand later, Alcaraz has two set points.

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

Image source, Getty Images

Alcaraz has the ability to throw in the occasional slices and loopy balls - he has so many layers to dip into.

He has caught Sinner out a few times with thumping forehands, and then takes the ball out of the air on the return to secure the point.

This is an efficient match and yet it is no less entertaining.

Yes he can.

Sinner holds serve and asks the question of Alcaraz.

The Spaniard will serve for the third set.

The last time Sinner lost a set 6-0 was against Daniil Medvedev at the tour finals in 2021.

Can he hold serve here to prevent it from happening in the US Open final?

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

Sinner is losing more control. Perhaps he is frustrated that he did not getting ahead earlier in this third set.

I am shocked. I did not predict this.

It looked like Sinner was claiming control of the match. He lost control of his emotions and he has not been able to get back from there.

Alcaraz is absolutely cooking right now and Sinner pings one wide as the Spaniard seals another hold and puts himself within one game of taking the third set and moving ahead in this final.

Sinner had only been broken four times across the fortnight until tonight.

He has now been broken four times in this match.