Coco Gauff battled through more serving problems to scrape into the second round of the US Open.
The French Open champion changed her coaching team on the eve of the tournament, adding biomechanics expert Gavin MacMillan in an effort to fix her serving issues.
Gauff hit 10 more double faults under the lights on Arthur Ashe Stadium, but avoided a repeat of her first-round Wimbledon exit, eventually defeating Ajla Tomljanovic 6-4 6-7 (2) 7-5 after two hours and 57 minutes.
"Mentally it's exhausting, but I'm trying," said Gauff of her attempts to improve her serve. "It wasn't the best today, but at 30-30 (in the last game) it came in when it mattered. It's an improvement.
"It was a tough match. I had chances for it to be straight sets. Ajla was tough, I felt like she was getting so many balls back. I'm happy to get through to the next round. I had so many chances. I was like, 'eventually they're going to come'."
Gauff led 4-2 in the second set before losing three games in a row and then served for the match at 5-4 in the decider only to double-fault twice in a row.
But the third seed broke Tomljanovic again to give herself a second chance and this time she took it, roaring after hitting a backhand winner down the line on match point to set up a second-round clash with Donna Vekic.
Naomi Osaka, who is seeded again at a grand slam for the first time since before her maternity break, moved into round two with a 6-3 6-4 victory over Greet Minnen, while Wimbledon runner-up Amanda Anisimova beat Kimberly Birrell 6-3 6-2.
Iga Swiatek set a new record with a dominant first-round victory over Emiliana Arango at the US Open.
The Wimbledon champion continued her impressive summer form with a 6-1 6-2 stroll against Colombian Arango on Arthur Ashe Stadium to cruise into round two.
Swiatek has now won her opening match at 65 consecutive tournaments, breaking the previous open era record set by Monica Seles.
While the Pole is seeded second behind Aryna Sabalenka, she appears to be the player to beat at Flushing Meadows, having followed up her Wimbledon triumph by winning the big WTA event in Cincinnati last week.
Swiatek seemed more excited about news of Taylor Swift's engagement than her own victory, but she was happy to have made a confident start.
"First matches are always a bit different, so I’m happy that I had some time to just get used to the conditions and the surface, because for sure it’s different than the practice courts," said the Pole, who won her only title here in 2022 and next faces Dutchwoman Suzan Lamens.
"I think it was just a solid match, and so I’m happy that I can play another round here."
Englishwoman
Sonay Kartal limped to defeat in an extraordinary opening-round clash with Beatriz Haddad Maia.
Kartal was making her debut in the main draw in New York following her speedy rise up the rankings and was looking to write more grand slam headlines following a run to the fourth round of Wimbledon.
She beat Haddad Maia earlier this season in Indian Wells but, inspired by her noisy Brazilian fan club, the 18th seed overcame cramp to claim a 6-3 1-6 6-1 victory.
The third set, which was delayed by a long bathroom break for Haddad Maia, provided high drama, with both women barely able to move.
Kartal, who appeared to be struggling with a recurrence of a knee problem, tried to find a way back after Haddad Maia suddenly began cramping leading 4-0, the Brazilian struggling just to roll serves over the net.
But Kartal was also clearly physically compromised and it was Haddad Maia who managed to stumble across the line.
England's Katie Boulter will drop outside the world's top 50 after also losing in the opening round.
Boulter has had a difficult season and admitted ahead of her meeting with Marta Kostyuk that she had begun to feel burnt out after heading straight from Wimbledon to the United States.
This was a tough draw against the 27th seed and Boulter was unable to prevent a first opening-round loss here in four years, losing out 6-4 6-4.
Tournament organisers announced, meanwhile, that Venus Williams, who impressed in a first-round defeat against Karolina Muchova on Monday, will play in the women's doubles with Leylah Fernandez.
