Image source, Getty Images

Marta Kostyuk speaking to Sky Sports after her win on Grandstand: "First of all, thank you guys for your support. It is my first ever win on this court. I'm really happy to close out this win after missing a number of match points."

On losing to Katie Boulter in the 2024 San Diego Open final: "That one was really tough. I can still remember that match and she was playing unbelievably well. It is a different day and a different year now, and it shows everything changes in tennis. I'm really glad I got this one."

On bringing her dog - Mander the Maltipoo - to this year's tournament: "He had a haircut yesterday. He is our biggest trophy, for sure. It is amazing to be able to travel with him. It is preparation for parenting for us. My team are also obsessed with him, so if I need a break then they are always happy to take him."

Some anxious moments for Sonay Kartal, who is not moving quite as freely in this game as she has previously.

Beatriz Haddad Maia tries to take advantage of that by moving Kartal around the court. Kartal gets to 40-30 but then nets to give Haddad Maia a 3-0 lead in the decider.

Is it just a bit of cramp for Kartal in the extreme heat, or is it something more serious?

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra and BBC Sounds

Haddad Maia took a long break and during that break Sonay was talking to her physio and pointed to her calf.

She's a little bit slack in her footwork, she wasn't quite on it and didn't move her feet quite the same, maybe she is feeling something.

And there's evidence of that as she stops abruptly during the first point of Haddad Maia's service game.

Sonay Kartal is broken to love by Beatriz Haddad Maia in her opening service game of the third set and the British player has work to do.

Awwww.

Marta Kostyuk's coach lifts up the Ukrainian's little dog - Mander the Maltipoo - who apparently just had a haircut yesterday and looks like he couldn't care less that his mum has just won her first-round US Open match.

Very, very cute.

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Iga Swiatek speaking to Sky Sports: "It felt great [out there], thank you guys for coming. For sure, first matches are not easy to get use to the rhythm and It was a solid match and I am happy that I wasn't trying to overpower and I was solid."

On her Polish fans: "Polish fans are everywhere and it is super nice to feel their support everywhere. I appreciate people that come from different countries and I just hope that they enjoy my game."

Swiatek will face Suzan Lamens in round two, after she beat American Valerie Glozman 6-4 6-2.

Beatriz Haddad Maia holds serve to 30 in the first game of set three, which draws a quick song from her supporters on Court 12.

Great Britain's Sonay Kartal takes a large swig of squash at the mini-changeover and prepares to serve for the first time in the decider.

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A fourth first-round exit for Katie Boulter on the hard courts this year.

It's been a tough old summer for the British number two.

She becomes the first Briton to fall at Flushing Meadows too.

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra and BBC Sounds

A tough one for Katie Boulter there. She didn't really get going until right at the end there, where it was more a case of her opponent handing her back some of the initiative.

She was 0-40 up in that game there to get it back to 5-5 in the second set - and who knows what could've happened then? It's the tale of her summer though.

Hm. All three break points are quickly wiped out and Marta Kostyuk earns a SIXTH match point.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

If you hang in against Kostyuk, you always have a chance.

The talented Ukrainian has a tendency to throw in a wobble - particularly on her serve.

Remember her match here against Britain’s Harriet Dart last year? It was messy…

Hello...

Katie Boulter's body language has indeed changed since she fended off those match points and she earns three break points as Marta Kostyuk serves for the match.

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra and BBC Sounds

Katie Boulter's body language has completely changed. She has saved five match points by scrapping, battling and being brave in defence.

From Marta Kostyuk's point of view, she will be thinking that she has missed five match points to close out a straight sets win. She will have to come out and serve for it now, which isn't easy.

It's going to be interesting this...

Beatriz Haddad Maia left the court at the end of the second set. Sonay Kartal is being sheltered from the sunshine by an umbrella as she sits and waits for her opponent to return.

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A tough task for Marta Kostyuk now, who will aim to serve out the match having missed five match points on the Katie Boulter serve.

Katie Boulter is hugely on the defence and it looks like Marta Kostyuk has the point won four or five times but she comes into the net and her over-zealous forehand can only crash into the barrier.

After five match points, Boulter finally finds a game point of her own and then sees out the service game with a forehand winner.

She has a bit more of a spring in her step heading back to her chair after surviving that.

Emiliana Arango forces the longest rally of the match but a superb volley at the net from Iga Swiatek helps her hold serve yet again.

The Colombian announces herself in to her service game with an excellent backhand but sees Swiatek fightback and convert a second break point.

The Pole will now serve for the match.

Image source, Getty Images

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Hmmm. My previous observation did not really stand the test of time.

Boulter is looking increasing frustrated now as she battles to stay in this match.

The British accents in the crowd are trying their best to encourage her, though.