It's all set up for Andrey Rublev to take control of this set but he wastes break point with an unforced forehand error.

That game saw the longest rally of the match, but Rublev didn't get the net cord as the ball bounces the wrong side.

Tristan Boyer recovers to stay on serve.

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

This is where we find out where Lamens' head is really at because we know that Swiatek is going to come back fighting.

But what we don't know is where her forehand is going to be.

Image source, Getty Images

Iga Swiatek had lost a grand total of five games in her previous three Grand Slam matches before today, and has now won 15 consecutive sets at the majors since dropping the opening set of her second-round match against Caty McNally at Wimbledon.

Will she make it 16 in a row? Well, the number two restores her break of serve on Arthur Ashe Stadium as Suzan Lamens nets on the first of two break points.

Is that the end of the wobble? An easy enough hold of serve for Iga Swiatek, wrapped up with an ace.

Tristan Boyer begins his service game with another double fault, but recovers to hold and take a 3-2 lead.

This is much better from the American.

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

Lamens is hitting the ball really well and she has managed in the 52 minutes they have been playing to push Swiatek back towards the baseline.

And now a comfortable hold of serve for Suzan Lamens, who is warming to her task a little bit and no doubt enthused by the struggles Iga Swiatek has had in the past few minutes.

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

Swiatek is looking towards her team, as if she is saying 'what is going on with my forehand?'

Slightly strange.

Lamens is going to be onto it now.

Spoke too soon - a break to love for Suzan Lamens.

Iga Swiatek throws in some errors, before Lamens produces another lobbed winner to wrap up the game.

Tristan Boyer holds again - he's hitting the ball with much more confidence and forcing Andrey Rublev into errors.

It didn't look like we'g get this response from Boyer after such a demoralising second set - could this be the start of something?

Suzan Lamens produces her best moment of the match as Iga Swiatek clips the top of the net with a backhand before approaching the net, and Lamens lifts it over her for a lovely lobbed winner.

Swiatek finds some success with her returns to earn a break point, though. A first one goes begging, a second one doesn't.

Swiatek in full control now against the world number 66.

Image source, Getty Images

Tristan Boyer takes the opening game of this must-win third set.

Andrey Rublev holds to take the second set.

Tristan Boyer made the perfect start to the second set by breaking, but Rublev hit back by winning the next four games to take control.

Boyer has really struggled with his second serve - he won just 27% of his second serves in the second set, compared to Rublev's 64%.

The American has also made four double faults today, while Rublev has committed none.

As well as Rublev is playing, Boyer isn't helping himself.

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

This is surprising and maybe Swiatek was playing a little too well in the first set.

Some more errors of the racquet of Iga Swiatek would also help Suzan Lamens find a way into this second-round match, and three of them give Lamens two break points.

Swiatek saves them both, though, before going on to level the second set.

Can Suzan Lamens find a way into this match? A comfortable hold of serve at the start of the second set would help - and that's exactly what she gets.

She puts away an overhead smash at the net for her first winner of the match to wrap up the game.

Two holds means Andrey Rublev remains in control and is now one break away from taking this second set.

Tristan Boyer's coach gave his player plenty of encouragement before the change of ends, telling the 24-year-old that he needs to up his game.

Two more unforced errors followed and Boyer has it all to do now.

Abigail Johnson
Commentator on BBC Radio 5 Sports Extra and BBC Sounds

The best front runner in the game is at it again.

Inside half an hour, Iga Swiatek is a set to the good on Arthur Ashe Stadium.

The world number two has had more unforced errors (10) than winners (nine) so far but she has still been far too good for Suzan Lamens.

Lamens has tried to extend rallies but has not hit a winner yet in the match.

Iga Swiatek finds her range on her returns to secure a double break and will expect to wrap up the first set in the next couple of minutes.