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British qualifier Jan Choinski narrowly loses to Roberto Carballes Baena in five-set thriller
Coco Gauff starts title defence in New York with 6-2 6-0 win over Varvara Gracheva
Alexander Zverev and Olympic champion Zheng Qinwen among early winners on Monday
2020 US Open champion Dominic Thiem loses in straight sets to Ben Shelton in final Grand Slam appearance
Novak Djokovic, Aryna Sabalenka and GB's Harriet Dart scheduled to play on day one
*Choinski 2-6 3-6 7-5 2-2 Carballes Baena
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
Jan Choinski is making the most of the second serve.
Whenever Roberto Carballes Baena takes just five percent off his serves here, Choinski is all over them.
He's not taking his foot off the gas.
*Choinski 2-6 3-6 7-5 2-2 Carballes Baena
Now it's Roberto Carballes Baena's turn to double fault before Jan Choinski steps into a powerful forehand and opens up two break points.
He takes them immediately with a huge forehand winner with Baena can only stand and watch.
As you were.
Choinski 2-6 3-6 7-5 1-2 Carballes Baena*
Roberto Carballes Baena is so deep in the court on Jan Choinski's serve you can't see him on the television cameras.
There he is though, stepping into vision as the Spaniard takes advantage of a second serve and opens up a break point.
Choinski then double faults to hand the break to Carballes Baena.
Just as it felt the Briton could be building some momentum...
*Choinski 2-6 3-6 7-5 1-1 Carballes Baena
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
Jan Choinski was looking tired but he has completely switched the energy and momentum of this match.
Roberto Carballes Baena is still up on the scoreboard but he will have to have more conversations with himself about being positive. He just needs to remind himself that he is two sets to one up.
US Open latest
Image source, Getty ImagesA quick update from around the courts at Flushing Meadows:
Zheng 4-6 6-4 6-2 Anisimova
Zheng Qinwen smiles broadly after coming through a hugely entertaining contest on Louis Armstrong Stadium against Amanda Anisimova.
Anisimova came out of the traps extremely quickly, led 5-1 and ended up taking the opening set.
However, Zheng fought back well, with her serve an especially powerful weapon, and the Olympic champion is through to round two.
"She was hitting the ball really good today, every ball went inside [the court] at the beginning and I couldn't do anything there," said Zheng in her on-court interview.
"The more the match went on, I began to find my rhythm and in the second set I started to be more consistent. Amanda had a really good performance today."
*Choinski 2-6 3-6 7-5 0-0 Carballes Baena
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
Jan Choinski has definitely loosened up feeling like it is now or never.
Just an incredible turnaround in the match.
He is still in this match, after being seemingly fatigued.
What a way to turn the match around, 17 winners from his racket in that third set.
*Choinski 2-6 3-6 7-5 0-0 Carballes Baena
Now then, a chance for Jan Choinski at 0-30 on Roberto Carballes Baena's serve.
A superb forehand which bites at the Spaniard's toes then opens up three break points for the Briton.
And he takes it at the third attempt with a deep forehand winner!
Where has that come from?
*Choinski 2-6 3-6 5-5 Carballes Baena
Roberto Carballes Baena doesn't give an inch as the Spaniard holds.
Both players are breathing a little heavier now as the sun continues to bake Court 16 at Flushing Meadows.
*Zheng 4-6 6-4 5-2 Anisimova
Image source, ReutersInto the net from Amanda Anisimova and Zheng Qinwen has a double break in the deciding set.
The Olympic champion is one game away from a place in the second round.
Choinski 2-6 3-6 5-4 Carballes Baena*
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
Everything is just falling into Jan Choinski's favour at the moment.
He's getting a little bit more on the second serves.
Choinski 2-6 3-6 5-4 Carballes Baena*
Jan Choinski responds with a speedy serve to love and he's potentially one game away from the third set.
He couldn't, could he?
*Choinski 2-6 3-6 4-4 Carballes Baena
Roberto Carballes Baena steams through a service game, holding to 15 with an ace.
That's his 15th of the match which is a record for the Spaniard.
Jan Choinski has been inconsistent today but take nothing away from Carballes Baena - he's more than played his part on the other side of the net.
BBC Radio 5 Sports Extra
Listen to live commentary of day one at the US Open on BBC Radio 5 Sports Extra and BBC Sounds using the link at the top of this page.
*Choinski 2-6 3-6 3-3 Carballes Baena
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
So often we can't even see Roberto Carballes Baena on our screen, he is so deep in the court, almost touching the back boards.
*Choinski 2-6 3-6 3-3 Carballes Baena
A fourth break point of the match for Jan Choinski - can the Briton take his first one?
Yes he can, although it is more handed to him as Roberto Carballes Baena double faults.
A tiny slither of hope for Choinski.
Zheng 4-6 6-4 2-0 Anisimova*
Image source, Getty ImagesIt's not just a probable blister on her foot that Amanda Anisimova is having to contend with, it's a rejuvenated Zheng Qinwen.
Having looked out of sorts in the early stages, Zheng is looking the favourite to go through to round two now.
The Chinese player broke Anisimova in the first game of the set and her serve is on point once more, Anisimova sending a second serve return into the tramlines to give Zheng a 2-0 lead.
Anisimova seems to have a problem with her right wrist, too.
Zheng 6-4 4-6 0-0 Anisimova*
David Law
Commentator on BBC Radio 5 Sports Extra and BBC Sounds
Amada Anisimova has had issues with blisters recently.
A lot of tennis, she reached the final in Canada. It is hot, it's sweaty. She has just put two sets in against Zheng Qinwen.
One set to go, it's a tough situation.
*Zverev 6-2 6-7 0-0 Marterer
A double fault at 5-5 in the tie-break proves costly for Alexander Zverev and the fourth seed loses the second set against fellow German Maximilian Marterer.
Still plenty of work for the 2020 runner-up to do if he's to reach the second round.
Choinski 2-6 3-6 1-2 Carballes Baena*
Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds
Roberto Carballes Baena is just giving absolutely nothing away.
If he can get his racquet on the ball, it is making it back on to court.