Russian No. 3 seed Daniil Medvedev retired after one set of his Mutua Madrid Open quarterfinal match Thursday in Spain, sending Czech No. 30 seed Jiri Lehecka to the first ATP Masters 1000 semifinal of his career.

Lehecka won the first set 6-4, but not before Medvedev began having issues with his upper right thigh. Medvedev sought treatment on his leg while leading the set 3-2 and needed treatment again with a 4-3 lead.

“Tough to say because when I stretch I don’t feel, but when I move I basically cannot move,” Medvedev told his trainer, according to the UK’s Metro Express.

Lehecka took over when he broke Medvedev’s serve in the ninth game en route to winning the final three games of the day. He had two aces and won 15 of his 16 first-service points.

“It’s never easy in a match like this,” Lehecka said post-match. “If I were to choose the way how to win this match, it wouldn’t be like that. So of course, it’s never easy to see your opponent struggling, but at that moment, you just need to focus on yourself, trying to get the maximum level out of yourself.”

Lehecka, 22, won his first ATP title earlier this season in Adelaide, Australia. He defeated Spanish star Rafael Nadal in the previous round of Madrid.

The men’s match schedule for Thursday was shorter than usual because No. 1 seed Jannik Sinner of Italy had previously withdrawn with a hip injury.

Canadian Felix Auger-Aliassime advanced to the semifinals via walkover. Now, he and Lehecka are slated to meet in one semifinal match, while No. 7 seed Andrey Rublev of Russia will oppose No. 12 seed Taylor Fritz in the other.

–Field Level Media