Serena Williams overcame an injury scare to maintain her pursuit of a record-tying 24th grand slam singles title at the US Open on Sunday while Roland Garros champion Ashleigh Barty and Karolina Pliskova crashed out in the last 16.
Williams, a six-time US Open winner, romped to a 6-3, 6-4 victory over Croatian 22nd seed Petra Martic to set up a quarter-final with China's Wang Qiang, the conqueror of world No 2 Barty.
The 37-year-old American required a medical timeout in the second set after rolling her right ankle as she approached the net but promptly recovered to reach the last eight in New York for the 16th time.
"I feel fine right now physically," said Williams, who received further strapping to an already heavily taped ankle. "But I'll see tomorrow. So far I'm good. I have been managing it. We'll see tomorrow.
Eighth-seeded Williams, who has also suffered knee and back injuries this season, felt a mental setback when it happened but battled through to win.
"I've had a rough year with injuries," she said. "It was like, 'Oh my God. Not again. I'm finally walking.'"
Williams, who last won a major at the 2017 Australian Open and hasn't won the US Open since 2014, is seeking a 24th career slam title to match Margaret Court's all-time record.
She will play 18th seed Wang for the first time as the Chinese 27-year-old extended her best Slam run with a 6-2, 6-4 defeat of an erratic Barty.
The Australian, who beat Wang twice last year in their only prior meetings, was undone by 39 unforced errors at Louis Armstrong Stadium.
"It's a tough day at the office today. But it has been a year where we've hit our goals," Barty said. "We've had a great season in Grand Slams for singles. We've made the second week every single one, which has been really special.
"Now we'll sit back, reflect, and look forward to a big couple months to finish off the year."
Wang became the first Chinese player to reach the women's quarter-finals since Peng Shuai made it to the last four in 2014.
"I think I'm really focused on the court, really enjoyed the way I played. I'm so happy I won," said Wang, whose breakthrough run has been fuelled by the memory of her late coach, Peter McNamara.
The former Australian Davis Cup star and Wimbledon doubles champion passed away in July at the age of 64 after a battle with prostate cancer.
"He helped me a lot. It was really tough to me to hear he passed," Wang said. "I think he has always been there with me."
Johanna Konta avenged her Rome final loss to Pliskova in May, beating the Czech third seed for just the second time in eight tries, 6-7, 6-3, 7-5.
The British 16th seed has raised her game at the slams this season, and is enjoying her best run at Flushing Meadows, having twice reached the fourth round.
"To go one step further is a massive achievement for me and I'm really hoping to make that one, two, three steps forward," Konta said.
Konta has experienced middling fortunes on the WTA circuit this year while producing some of her best tennis at the majors, reaching the semi-finals at Roland Garros and then advancing to the last eight at Wimbledon.
"To make the quarter-finals of a Grand Slam for the third time this year is a massive achievement for me," she said.
Pliskova, the 2016 US Open runner-up, saw her hopes of returning to world number one this fortnight extinguished by the loss.
Ukrainian fifth seed Elina Svitolina advanced to her first US Open quarter-final with a 7-5, 6-4 victory over 2017 runner-up Madison Keys.
"I'm very happy because I was always playing well here but never went past the fourth round," said Svitolina, whose best slam showing was her run to the Wimbledon semi-finals in July.