Angelique Kerber won a matchup of previous US Open champions Friday, while Garbine Muguruza and Simona Halep might finally have the answers for the hard courts in the year's final Grand Slam tournament.
Kerber, the 2016 champion, was ruthless in the third set to knock out 2017 champion Sloane Stephens 5-7, 6-2, 6-3 and reach the fourth round in New York.
The 16th-seeded Kerber beat Stephens for only the second time in seven career matchups. The 33-year-old Kerber won for the second straight day and laughed when she said she could use the day off Saturday.
Muguruza beat three-time US Open finalist Victoria Azarenka 6-4, 3-6, 6-2 to match her best showing in New York, and Halep fought through a marathon first-set tiebreaker and eventually beat Elena Rybakina 7-6 (11), 4-6, 6-3 to reach the fourth round for the first time since 2016.
The No. 9 seed from Spain, Muguruza reached the round of 16 in 2017, right after winning her Wimbledon title. She hadn't been past the second round since, although she said she always liked playing in New York despite her struggles.
"The past years I was very -- in Spanish we say you're a little bit cross, your brain is a little bit not working very well," Muguruza said. "I felt, yeah, I don't know, negativity was more than positivity in the previous years.
"This year, I don't know, I just prepared well and say, 'Hey, at some point it's going to change.' This might be the year."
Halep had lost in the US Open first round in 2017 and 2018 -- the latter the first time that had happened to the No. 1 seed in the first round at the tournament -- and her success this time was tough to expect after she missed Wimbledon and the French Open with a calf injury.
Halep, the No. 12 seed from Romania, needed seven set points to finally win the tiebreaker after she was broken at love when serving for the set at 6-5.
She eventually won it when 19th-seeded Rybakina double-faulted, working her way to the round of 16 for the first time since reaching the quarterfinals in 2016.
"I know that every match is a battle," Halep said. "But I'm there, and if I'm healthy, I'm confident that I can play my game."
Aryna Sabalenka is on her way to face her Grand Slam doubles championship partner after she knocked off Danielle Collins 6-3, 6-3 at Louis Armstrong Stadium. She's into the second week of the U.S. Open for the first time since 2018.
The second-seeded Sabalenka has a quarterfinal matchup against Elise Mertens, with whom she won the 2019 US Open women's doubles title. They also won the 2021 Australian Open doubles championship.
Sabalenka has won five of the seven career meetings against Mertens.
French Open champion Barbora Krejcikova is also into the fourth round in her US Open debut. The Czech player, who is seeded eighth, beat Kamilla Rakhimova 6-4, 6-2 to set up a fourth-round meeting with Muguruza.
Krejcikova improved to 41-11 this season. Only top-ranked Ash Barty (42-7) has more wins in main draw matches on the women's tour.
No. 5 Elina Svitolina defeated No. 25 Daria Kasatkina 6-4, 6-2.
The Associated Press contributed to this report.