Novak Djokovic has been forced to withdraw from the French Open due to a right knee injury, tournament organisers announced on Tuesday.
Djokovic will thus be unable to defend his title and also relinquishes his No1 ranking, with Jannik Sinner set to eclipse him and become the first ever Italian to top the men's rankings.
The Serbian great was supposed to face two-time French Open runner-up Casper Ruud in the quarter-finals on Wednesday.
However, there was a question mark over the contest as Djokovic had suffered a knee injury during his five-set win over Francisco Cerundolo on Monday.
Early in the second set, 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 any inflammation.
Djokovic revealed after the match that he would undergo a scan to determine whether he would be able to continue at the tournament.
The 37-year-old blamed the "slippery" surface on Court Philippe-Chatrier for the injury.
"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 had said after the match.
"I'm glad that I was able to play the fifth set and last three, four games of the fourth without feeling that pain that I felt for two-and-a-half sets."
The MRI scan revealed the Serb tore the medial meniscus in his right knee, forcing him to pull out.
Roland Garros organisers said: "Due to a torn medial meniscus in his right knee (discovered during an MRI scan performed today), Novak Djokovic, who was supposed to play Casper Ruud in the quarter-finals tomorrow, has been forced to withdraw from the Roland-Garros tournament."
Norwegian seventh seed Ruud will progress straight to the semi-finals. Djokovic's withdrawal also means Sinner will become world No 1 at the end of the tournament.
Sinner already knew that he could secure top spot by reaching the final at Roland Garros, but his landmark achievement was secured earlier than expected.
The 22-year-old has enjoyed a fine season, also winning the Rotterdam and Miami Opens in addition to his maiden Grand Slam title in Melbourne.
With Djokovic's exit, the tournament lost most of its star power. Earlier, Rafael Nadal's record-breaking French Open career came to a likely end when the 14-time champion slumped to a demoralising first-round defeat against Alexander Zverev.
Nadal, who turns 38 on June 3, went down 6-3, 7-6 (7/5), 6-3 to world No 4 Zverev, suffering only his fourth loss in 116 matches at Roland Garros since his 2005 title-winning debut.
