PARIS, France (AFP) — Novak Djokovic pulled out of the French Open on Tuesday ahead of his quarterfinal against Casper Ruud because of a knee injury suffered in the previous round.

“I am really sad to announce that I have to withdraw from Roland Garros,” Djokovic wrote on social media.

“I played with my heart and gave my all in yesterday’s match and unfortunately, due to a medial meniscus tear in my right knee, my team and I had to make a tough decision after careful consideration and consultation.”

Tournament organizers had initially announced his withdrawal, saying an MRI scan earlier on Tuesday had revealed the full extent of the injury.

World No. 1 and 24-time Grand Slam champion Djokovic was due to play Ruud on Wednesday for a place in the last four. Djokovic defeated Ruud in straight sets in last year’s final at Roland Garros.

As a result, Ruud will go on to face fourth seed Alexander Zverev or 11th seed Alex de Minaur in the semifinals on Friday.

‘I am really sad to announce that I have to withdraw from Roland Garros.’

The 37-year-old Djokovic had cast doubt over his fitness following Monday’s five-set win over Francisco Cerundolo, admitting he needed anti-inflammatory drugs to get through the match.

Djokovic blamed the “slippery” Philippe Chatrier court for the injury he sustained early in the second set of his 6-1, 5-7, 3-6, 7-5, 6-3 victory over Cerundolo.

“I don’t know what will happen tomorrow or after tomorrow if I’ll be able to step out on the court and play. You know, I hope so. Let’s see what happens,” Djokovic said after his record 370th win at a Grand Slam.

“For the last couple weeks I have had, I would say, slight discomfort, I would call it that way, in the right knee, but I haven’t had an injury that would be concerning me at all.”

“I was playing a few tournaments with it, and no issues until today.”

Djokovic had already been tested to the limit physically by a grueling four-hour, 29-minute slog against Lorenzo Musetti in the third round that concluded at 3:07 a.m. Sunday morning, the latest finish in French Open history.