Canadian teen Leylah Fernandez followed her shock upset of 2020 U.S. Open winner Naomi Osaka by defeating German 16th seed and three-time Grand Slam champion Angelique Kerber 4-6, 7-6 (7/5), 6-2.
"I just tried to use all my trainings from back home," Fernandez said. "They told me take it point by point. I was glad I was able to execute it."
Seven of the top nine women's seeds reached the last 16, with Osaka and top-ranked Wimbledon champion Ashleigh Barty exiting early.
Fernandez, who turns 19 on Monday, advanced to a first Slam quarter-final against Tokyo Olympic bronze medalist Elina Svitolina, the fifth seed from Ukraine.
Svitolina, who turns 27 next Sunday, beat two-time major winner Simona Halep 6-3, 6-3 to reach her eighth Grand Slam quarter-final. Svitolina, coming off a WTA title in Chicago, stretched her win streak to nine matches.
"That's going to be a very tough match," Fernandez said. "She returns a lot of balls. She's aggressive. I'm just going to go on court and try to keep doing what I've been doing."
Second seed Aryna Sabalenka of Belarus, who made a Slam-best run to July's Wimbledon semi-finals, eliminated Belgian 15th seed Elise Mertens 6-4, 6-1.
Sabalenka will next face Czech eighth seed Barbora Krejcikova, the reigning French Open champion who held on to beat two-time Grand Slam champion Garbine Muguruza 6-3, 7-6 (7/4).
Krejcikova led a set and two service breaks before Muguruza rallied.
But the Spaniard could not convert three set points in the 10th game of the second set and Krejcikova then came back strong after a medical timeout off the court to treat what she told the umpire was trouble with her diaphragm.
Muguruza, apparently annoyed by the time Krejcikova took between points during the remainder of the match, offered a chilly handshake at the net and departed before Krejcikova, breathing hard, made her way from the court escorted by a trainer and doctor.
