World Jannik Sinner has withdrawn from the Cincinnati Open with a right knee injury.

He joins world No. 2 and defending champion Carlos Alcaraz, who also pulled out.

"After consulting with my doctors and my team, I have to announce that I need to withdraw from the Masters 1000 tournament in Cincinnati," Sinner said. "My right knee has been bothering me and even though we have been working hard with my medical team, I have to accept that I’m not ready to compete yet.

“I’m very disappointed not to be able to play in Cincinnati and wish Bob [Moran] and his whole team a great and successful event. I can’t wait to be back next year and I’m now focusing on getting ready for the U.S. Open.”

The Cincinnati Open will begin Tuesday, Aug. 11, with the qualifying tournament and continue through Finals Weekend culminating with the singles championship matches on Sunday, Aug. 23.

The draw ceremony for the Cincinnati Open will take place Tuesday at 3 p.m. local time.

Novak Djokovic is set to compete for the first time since Wimbledon, while top seed Alexander Zverev will look to bounce back from an opening-round exit in Montreal and will be the top seed at the hard-court event.

Cincinnati main-draw action will take place from Aug. 13-23. Three-time winner Djokovic, Zverev, Daniil Medvedev, Grigor Dimitrov and Marin Cilic are among the former champions in the draw.

The U.S. Open begins Aug. 30 and the world’s top two players have now withdrawn from the preeminent hardcourt warmup tournament ahead of the year’s final major.

(The ATP contributed reporting).