Top-seeded Alexander Zverev kept his bid for a first US Open title on track with a gritty five-set victory over Quentin Halys, staying the course as a spate of upsets rocked the men's draw on Thursday.
A trio of former women's champions – Coco Gauff, Iga Swiatek and Naomi Osaka – booked third-round berths, along with reigning Grand Slam champions Elena Rybakina and Mirra Andreeva.
But men's third seed Felix Auger-Aliassime tumbled out, along with sixth-seeded Alex de Minaur and 13th-seeded Lorenzo Musetti.
Zverev labored util 2:15 am Friday on Arthur Ashe Stadium to shake off 52nd-ranked Frenchman Halys 6-4, 4-6, 7-6 (7/3), 6-7 (3/7), 6-3.
The four-hour 33-minute marathon followed his wild first-round five-setter against 89th-ranked Lorenzo Sonego that kept Zverev at it until shortly before 2 am on Wednesday.
"The performance was quite shit to be honest, but I won, that's the most important thing," Zverev said afterwards.
"Physically, I feel fine. I am proud, I think, to be physically quite strong. I just hope at some point I'll start playing better tennis.
"I'm winning ugly right now. It's also a skill to win ugly and when you're not playing great tennis. I think I've mastered that right now."
While Zverev survived, Auger-Aliassime fell 6-7 (5/7), 6-3, 6-2, 6-2, to 50th-ranked Russian Karen Khachanov, pulled away relentlessly from the physically ailing Canadian, who said he was "dizzy and seeing spots.
"I thought maybe it would pass, but it didn't," a dejected Auger-Aliassime said.
Khachanov took full advantage of 47 unforced errors, with eight double faults, from Auger-Aliassime, who struggled particularly on serve.
"I thought maybe he had some physical issues, it's part of our sport," Khachanov said. "From my side I tried to give my best performance, fighting, fighting."
De Minaur fell to Botic van de Zandschulp 6-4, 7-5, 6-2 while 123rd-ranked Australian Dane Sweeny shocked 13th seed Musetti 3-6, 6-1, 6-2, 6-2 to reach the third round of a major for the first time.
It's not the first time Van de Zandschulp has sprung an upset at Flushing Meadows, where he shocked Carlos Alcaraz in the second round in 2024.
WOMEN CONTENDERS MARCHED ON
Fourth-seeded Gauff, the 2023 champion, thrilled the Ashe night crowd with a 6-4, 7-6 (7/5) victory over former world No 2 Paula Badosa of Spain.
Swiatek sailed through with a 6-3, 6-2 victory over Nadia Podoroska while Osaka survived a second-set swoon to beat Katerina Siniakova 6-2, 5-7, 6-1.
Australian Open winner Rybakina, the world No 2 who is closing in on Aryna Sabalenka's No 1 ranking, saw off Spain's Jessica Bouzas Maneiro 6-2, 6-4, and Andreeva rolled over Germany's Eva Lys 6-0, 6-2.
Gauff, 22, had lost five of her eight prior meetings with Badosa, so she was ready when the Spaniard piled on the pressure in the second set, regaining a break to force the tiebreaker.
"I knew she would raise her level. She's capable of blasting winners and blasting return winners," said Gauff, who was pleased she kept her composure.
"I think I need matches like this to build my confidence," the 2023 US Open winner said.
Swiatek, whose six Grand Slam titles include the 2022 US Open, had things mostly her own way against Podroska, a former top-40 player now 449th in the world.
She fought off four break points at 5-3 in the first set then pulled away to polish off the win in little more than an hour.
Japan's Osaka, who counts two US Open titles among her four majors, looked in total control against Siniakova as she raced through the first set and to a 4-2 lead in the second without facing a break point.
But the Japanese star's unforced errors began to pile up and doubles world No 1 Siniakova pounced to climb from 5-3 down and take the set.
Osaka regrouped in the decider, riding a quick break to a 3-0 lead and fending off a pair of break points on the way to victory.
"I just felt like I had to fight," she said.
So did former Australian Open champion Madison Keys, who saved five match points to beat Anna Bondar 4-7, 6-4, 7-6 (10/5).
There was a bittersweet goodbye on Louis Armstrong Stadium, where 20-year-old American Learner Tien ended 40-year-old Gael Monfils's Grand Slam career with a 6-3, 6-4, 6-3 victory.
"It's been a long ride," Monfils told an adoring New York crowd. "You are my second best crowd. Of course, it can't top Paris, but you are up there!"