Sloane Stephens defeated Garbine Muguruza in the pick of the fourth-round matches at the French Open on Sunday.
American Stephens, runner-up at Roland Garros last year, came from a break down in the first set to beat the 2016 champion 6-4 6-3 on Court Philippe-Chatrier.
The seventh seed will face the resurgent Johanna Konta in the quarter-finals after the Australia-born Briton got the better of Donna Vekic 6-2 6-4.
Petra Martic, who knocked out Karolina Pliskova in round three, came from behind to defeat Kaia Kanepi 5-7 6-2 6-4 and set up a clash with teenager Marketa Vondrousova after the 19-year-old beat 12th seed Anastasija Sevastova 6-2 6-0 in under an hour.
MUGURUZA MISSES CHANCE
Muguruza started her meeting with Stephens by sealing a break to love, but she missed five opportunities to take the seventh seed's next service game.
Stephens punished the Spaniard by rallying back to take the opening set and she did not face another break point until she was in position to serve out the match.
Muguruza managed to stave off four match points but missed her chance to restore parity and the 2017 US Open winner subsequently moved into the last eight.
TWO IN-FORM OUTSIDERS MEET
Vondrousova and Martic will both be making their maiden grand slam quarter-final appearances when they meet in the next round, and they can be considered the two most dangerous players on the WTA Tour at the moment.
Nobody has racked up more wins than Vondrousova since this year's Australian Open - her victory over Sevastova was her 25th in that span and booked a sixth successive last-eight appearance.
The unseeded Czech has won 13 matches on clay in 2019, but the only woman with more is Martic (15) and one of those came when she triumphed in their previous meeting in the final of the Istanbul Cup in April.
NO STOPPING KONTA
Konta continued her impressive season on clay by defeating fellow seed Vekic on Court Suzanne-Lenglen.
The 28-year-old had never won a match at Roland Garros before this year, but appeared to be feeling more comfortable on the surface as she made runs to the finals in Rabat and Rome.
Konta was modest when asked about what has changed to help her reach the quarter-finals of a grand slam for the first time since Wimbledon in 2017.
She said: "I think the level is quite similar. I think more than anything I am just playing the game quite well. I think that also comes from winning some matches, and you get some match fitness in. So I think similar, maybe just with an added bit of match fitness."