The tournament announced the news, saying Djokovic has a torn medial meniscus in his right knee. The extent of the injury was found during an MRI exam a day after Djokovic was hurt during a fourth-round victory against No. 23 Francisco Cerundolo that lasted five sets spread across more than 4½ hours.

The 24-time Grand Slam champion was supposed to face two-time French Open runner-up Casper Ruud in the quarterfinals on Wednesday. Instead, Ruud gets a walkover into the semifinals, where he will face No. 4 Alexander Zverev or No. 11 Alex de Minaur.

Djokovic’s knee had been bothering him for a couple of weeks before he arrived at Roland Garros — something he kept to himself until after the win against Cerundolo. Early in the second set Monday, Djokovic tweaked his knee and took a medical timeout. A trainer worked on the joint then and during subsequent changeovers, and Djokovic took what he said a tournament doctor told him was the maximum dose of pills allowed to dull the pain and reduce inflammation.

“I don’t know what will happen tomorrow — or after tomorrow, if I’ll be able to step out on the court and play,” the 37-year-old Djokovic said after Monday’s win. “You know, I hope so. Let’s see what happens.”

He needed to get back to the title match in Paris to retain his hold atop the ATP rankings. With the withdrawal, he now will be replaced by current No. 2 Jannik Sinner, an Italian who was playing his quarterfinal on Tuesday.

Fendrich writes for the Associated Press.