Jannik Sinner will be the new world number one after Novak Djokovic was forced to withdraw from the French Open due to a knee injury.

The Serb was forced to go the distance in his fourth-round tie against Francisco Cerundolo on Monday, coming from behind to win in five sets after just over four and a half hours on the court.

After cruising through the first set, Djokovic had to receive medical treatment in the second due to a knee problem but carried on, eventually receiving medication for the issue.

He revealed after the match that he was close to quitting due to the injury, and said he would make a decision on whether to continue on Tuesday.

The 37-year-old was due to face Casper Ruud in the quarter-final in a rematch of last year’s final, but instead, the Norwegian will advance with a walkover.

Djokovic had to reach the final to ensure he retained his world number one status, but his withdrawal now means Sinner will move above him in the standings after the tournament.

He will become the first Italian player to become world number one since the ATP rankings were published in 1973, with the change officially happening on June 10.

Sinner booked his place in the semi-finals on Tuesday after beating Grigor Dimitrov in straight sets.

There will also be a new champion at Roland Garros as Djokovic will not have the opportunity to defend his title or gain a 25th major title.