Serena Williams suffered an injury scare as she progressed to the last eight of the US Open with a straight-sets win over Petra Martic.

Though she was broken early in the match, Williams never really looked troubled by Martic as she won her 99th match at the US Open.

That tally is her most at a grand slam, but the 23-time major winner's triumph was not without drama as she rolled her ankle in the second set when going to the net.

Williams had to take a medical timeout but said she felt "good" afterwards, and her spirits will likely have been boosted by the exits of Ashleigh Barty and Karolina Pliskova.

BARTY PUTS IT IN PERSPECTIVE

Barty was stunned by Wang Qiang in her fourth-round clash, the second seed making 39 unforced errors in a highly disappointing display.

Wang claimed a 6-2 6-4 win, denying Barty the chance to play Williams in the quarter-finals, but the French Open champion was able to look back on her grand slam season with satisfaction.

"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," Barty told a media conference.

"Now we'll sit back, reflect, and look forward to a big couple months to finish off the year."

DOUBLE CELEBRATION FOR SVITOLINA

Elina Svitolina, meanwhile, saw off American Madison Keys in straight sets.

Svitolina is in a relationship with Gael Monfils, who watched on in Arthur Ashe Stadium.

Monfils turned 33 on Sunday, and Svitolina revealed she was inspired by playing on his birthday.

"It's his birthday, I was trying to be really focused on my match but it was extra motivation for me," Svitolina told ESPN on court afterwards.

LAST EIGHT IS GREAT FOR KONTA

Johanna Konta outlasted third seed Pliskova in an engrossing match on Louis Armstrong, producing a fine comeback to prevail 6-7 (1-7) 6-3 7-5.

It means the Briton has now reached the last eight of every slam in her career.

Konta is also the first British woman to reach this stage at the US Open since Jo Durie in 1983.

"I'm really pleased [with that achievement]," Konta said at a media conference. 

"I think for me more on a personal level to be able to have made it to the quarters for my third slam in a row, I think that's a really, really big achievement for me. So I'm really pleased with that."