Jeff Tarango
Former American tennis player on BBC Radio 5 Live

When Kostyuk won that second set she was all smiles, giggles and laughing and her smile has really gone away.

Wow, this is tense!

Marta Kostyuk offers an immediate response to falling behind in the third set - although she is certainly helped by a couple of big misses from Linda Noskova.

But Kostyuk can't build on that and is soon facing more break points. The Ukrainian saves the first two, but a big forehand from Noskova puts the sixth seed back in charge.

Image source, Getty Images

Carlos Alcaraz turns it on when it really matters at the end of the set.

He ramped up the pressure on Tommy Paul and the American just couldn't cope on this occasion.

He saves the first set point with a huge 136mph ace out wide and is aggressive on the next point, too, as he knows he needs to be.

But his blistering forehand is just wide and the defending champion is a set to the good.

Jeff Tarango
Former American tennis player on BBC Radio 5 Live

Paul has just been shaken a little bit by what Alcaraz has just done. Paul's done nothing wrong, he just can't live with this level from Alcaraz.

"Vamos!" cries Carlos Alcaraz.

He's on the attack against the Tommy Paul serve and moves up 0-30 again.

Paul finds the net again and Alcaraz has three break - and set - points.

Pressure on after losing the first point on serve at a crucial stage in the set?

Not if you're Carlos Alcaraz. He comes in behind a big serve out wide and powers a drive volley down the line for a winner.

He goes on to hold to 15 and Tommy Paul will serve to extend the first set.

Who will deliver the next twist in this engrossing fourth-round contest?

Marta Kostyuk has already escaped two match points to recover from 5-4 down in the second set and take her match against Wimbledon champion Linda Noskova to a decider.

Noskova, desperately needing to quickly move on from that disappointment, is the first to come under pressure in the third set but holds from deuce.

The sixth seed closes here eyes and breathes a sigh of relief.

Then, it's Kostyuk's turn, as a 40-15 lead evaporates.

A wide forehand gives Noskova the first opportunity of this set... and concedes with another miss!

Kostyuk can't believe it. She's going to have to come from behind again.

Image source, Getty Images

Tommy Paul gets himself out of trouble.

He wins the next four points and still we haven't seen so much as a single break point.

Carlos Alcaraz will be disappointed because he had a couple of looks at the second serve but couldn't capitalise.

Here's the opening for Carlos Alcaraz.

An unforced error from Tommy Paul - sending a forehand into the net - and it's 0-30...

Jeff Tarango
Former American tennis player on BBC Radio 5 Live

I think Kostyuk was the favourite at the beginning and now again she's the favourite after losing two match points. It's like a new lease of life.

It isn't a Grand Slam final, which means there won't be as many nerves on Kostyuk. It's almost a pattern for Noskova to do this to get ahead.

The first point of the game sees Tommy Paul go toe-to-toe with Carlos Alcaraz in a pulsating rally - and the American comes out on top.

That only seems to anger Alacraz, though, and he reels off the next four points in quick time.

An awkward serve into the body clinches the hold of serve.

Jeff Tarango
Former American tennis player on BBC Radio 5 Live

Alcaraz just looks like he's having a stroll in the park so far, walking around.

A thumping ace down the middle looks to have set Tommy Paul up for a comfortable hold of his own.

However, he goes long with a forehand and Carlos Alcaraz sees a chance.

The Spaniard shows his immense power from the back of the court to take it to deuce.

It's Paul's turn to dig in and he hammers down another big serve to keep it on serve.

Image source, Getty Images

Jeff Tarango
Former American tennis player on BBC Radio 5 Live

Alcaraz doing a little bit of the approaching there, taking a risk. A good approach, Paul has hit that passing shot, a little slice and didn't expect his opponent to be coming in.

The simplest hold of the match for either player sees Carlos Alcaraz hold to 15.

Still on serve in the first set.

Image source, Getty Images

Goodness me. We're in for a treat the way these two are playing!

It's Carlos Alcaraz's turn to draw gasps from the crowd with a forehand lasered millimetres over the net and past Tommy Paul for a winner.

And another! This is ridiculous.

Paul is still offering plenty himself and the American shows brilliant touch at the net on the way to holding serve.

David Law
Commentator on BBC Radio 5 Sports Extra

If these fans don't get much of a competitive match overall, they're at least going to go home with some of the highlight reel shots of the tournament so far.

Including one that has just been hit by Paul, around the net post and umpires chair, can't be more than a couple of feet between the two.

Image source, Reuters

Wow.

Marta Kostyuk was facing two match points about five minutes ago, now she's won the second set and levelled the match!

Four games in a row from the Ukrainian from 5-3 down, and a break to love to end the set.

Tommy Paul is wowing the crowd in New York!

After a lovely drop shot helps win him a point early in the game, he then shows his power with a blistering backhand that nearly takes the racquet from Carlos Alcaraz's hand.

Then he tops it all off with searing forehand from out wide, round the net post and just finding the corner. Brilliant.

But, even after all that, Alcaraz holds.

Image source, Getty Images

All the momentum is now with Marta Kostyuk, who has a spring in her step as she heads to her chair at the change of ends with a 6-5 lead and the chance of a free swing in the next game.

She'll have a tie-break in set two at the very least.