WIMBLEDON, England -- Madison Keys has a big, thumping game that seems to be made for grass. And yet Wimbledon is the only one of the four Grand Slams in which she hasn’t advanced to at least the semifinals.

Perhaps in this, her ninth appearance at the All England Club, that’s about to change. Keys’ 6-4, 6-1 victory Saturday over unseeded Marta Kostyuk thrust her into the second week of play. The No.25 seed meets the winner between No.22 Anastasia Potapova and 16-year-old sensation Mirra Andreeva -- a match that was postponed until Sunday because of rain -- in a fourth-round encounter Monday.

Wimbledon: Scores | Draws | Order of play

The 28-year-old American’s best previous result here was a quarterfinal finish in 2015.

Keys’ serve is the thing that usually pays the bills, but against Kostyuk she returned exceptionally well, breaking her five times and winning 30 of 58 of her return points.

Kostyuk was one of three Ukraine women, along with Elina Svitolina and Lesia Tsurenko, to reach the third round -- a first at Wimbledon. She was trying to match her best previous result at a Grand Slam, the fourth round two years ago at Roland Garros.

Wimbledon: Day 6

Kostyuk was 1-7 versus Top 20 players coming into the tournament but then managed to beat No.8 Maria Sakkari after losing the first set 6-0. Keys, ranked No.18, would have given her a second straight Top 20 win.

Keys broke Kostyuk to take a 2-1 lead but gave it right back when Kostyuk converted her seventh break-point opportunity in the game. Naturally, Keys came right back to go up 3-2 with a love return game. That proved to be the difference in the set. Not only did Keys break Kostyuk twice, but she also saved 10 of 11 break points against her.

Keys’ breaks in the second set came in the third, fifth and seventh games -- the last to close it out.