Novak Djokovic says it was a "tough decision" to pull out of the French Open tennis after picking up a knee injury.
The defending champion looked visibly in pain during his marathon five-set match against Argentina's Francisco Cerundolo on Monday.
He says it was a difficult game to get through.
Advertisement
The withdrawal now means Italian Jannik Sinner is the new men's world number one.
Quarter final action continues at the French Open in Paris today.
Alexander Zverev plays Alex de Minaur in the men's singles - while in the women's singles, Aryna Sabalenka faces Mirra Andreeva and Elena Rybakina takes on Jasmine Paolini.
