Defending champion Aryna Sabalenka received a walkover into the U.S. Open semifinals after Marketa Vondrousova was forced to withdraw from their last eight showdown due to injury, organisers said on Tuesday.

Vondrousova, the 2023 Wimbledon champion, had impressed in New York with upset victories over seventh seed Jasmine Paolini and ninth seed Elena Rybakina, but her run came to a painful end after she pulled up in practice earlier on Tuesday.

ESPN showed footage of the 26-year-old bending over in pain after hitting a forehand, before leaving the practice court in tears.

It was not immediately clear what the injury was.

It marked another cruel blow for the Czech, who has endured long stretches away from the tour due to shoulder problems, missing last year’s U.S. Open and January’s Australian Open.

She was one of three Czech women to reach the quarterfinals at Flushing Meadows.

“It’s so tough to see,” Sabalenka wrote on Instagram.

“So sorry for Marketa after all she’s been through. She has been playing amazing tennis, and I know how badly this must hurt for her,” she added.

Sabalenka became only the third woman in the professional era to receive a walkover into a Grand Slam semifinal, joining Arantxa Sanchez Vicario (Australian Open 1992) and Fabiola Zuluaga (Australian Open 2004).

Top seed Sabalenka will now face American Jessica Pegula in the semifinals, setting up a rematch of last year’s final.