Aryna Sabalenka has advanced to the US Open semifinals after Marketa Vondrousova withdrew with a knee injury.

“I regret to announce that I have to withdraw from my quarterfinal match tonight due to a knee injury. I did everything I could to get on the court today, but during the warm-up I felt my knee again and after consulting with the tournament doctor I decided not to risk aggravating the injury,” said the 26-year-old Czech.

Vondrousova, who has been struggling with a shoulder injury for a long time, has been playing excellent tennis in recent days. The Czech arrived in New York ranked No. 60 but emerged as one of the tournament’s pleasant surprises after eliminating two Top 10 players in back-to-back matches, Jasmine Paolini and Elena Rybakina.

Sabalenka, the reigning women's champion, will play fourth-seeded American Jessica Pegula in the semifinals on Thursday.

The American surprisingly easily eliminated Czech Barbora Krejcikova in the quarterfinals, 6-3, 6-3. The match lasted just one hour and 27 minutes.

Both sets played out in exactly the same way. Pegula led 4-1, Krejcikova fought back to cut it to 3-4, but the former Wimbledon champion immediately let her serve slip again, leading the American to victory. | BGNES