Top-ranked Karolina Pliskova advanced to the fourth round of the U.S. Open on Saturday, but the Czech star had a lot more trouble than expected in her third-round match.
Pliskova, a finalist at this tournament a year ago, had beaten 27th-seeded Shuai Zhang of China in all four of their previous meetings, including a 6-2, 6-0, 55-minute demolition on hardcourts in their only meeting this year.
On Saturday, however, Pliskova had to save a match point against her in the second set before rallying for a 3-6, 7-5, 6-4 victory.
"I think I'm playing in quite big waves this tournament so far," said Pliskova. "So I think sometimes I think I play good shots, good rallies, and then there is hundreds of mistakes and not a good shot."
"I just try to fight even if my game is not 100 percent, and it's not 100 percent, actually, this week. "But I'm winning, so that's the main thing."
Pliskova committed 14 unforced errors in the first set won by Zhang, who served for the match at 5-4 in the second set.
Zhang got to match point when Pliskova hit a backhand into the net. But Pliskova saved it with a big forehand that Zhang could not handle.
"If you're match point down, you don't really think, like, about what to play or if to hold it in the rally, so I didn't have any other choice," Pliskova said. "I just went through it and prayed that it's going to be in, and it was in."
Pliskova was able to hold on from there for the victory.
Pliskova's next match will be against Jennifer Brady, one of two Americans who advanced to the fourth round during the day matches, with Madison Keys scheduled to play a night match.
Brady, who is ranked 91st in the world, defeated Monica Niculescu of Romania 6-4, 3-6, 7-6 (3).
The other American who won Saturday was 20th-seeded CoCo Vandeweghe, who upset 10th-seeded Agnieszka Radwanska of Poland 7-5, 4-6, 6-4, to reach the fourth round of the U.S. Open for the first time in her career.
Vandeweghe's fourth-round foe will be Lucie Safarova of the Czech Republic, who got past Kurumi Nara of Japan 6-3, 6-2.
Fourth-seeded Elina Svitolina also advanced, beating Shelby Rogers of the United States 6-4, 7-5.
The Ukrainian converted her fourth match point to keep alive her hopes of being the World No. 1 after the tournament ends.
Unseeded Daria Kasatkina of Russia pulled off an upset, beating 12th-seeded Jelena Ostapenko of Latvia, this year's French Open champ, in relatively easy fashion 6-3, 6-2.
It was the second straight time Kasatkina had beaten Ostapenko after getting the better of her in Charleston in April.
In another third-round match pitting two unseeded players Kaia Kanepi of Estonia eliminated Naomi Osaka of Japan 6-3, 2-6, 7-5. The 32-year-old Kanepi is ranked 418th in the world, and she will try to keep her surprising run going when she meets Kasatkina in the round of 16.