The star power at the Cincinnati Open—and potentially the US Open—has taken another hit.

On Sunday, Jannik Sinner withdrew from the Ohio-based tournament, citing issues with his right knee. In a statement released by the tournament, the ATP’s No. 1–ranked men’s player expressed hope that he’ll be able to play in the US Open, which is set to begin its main draw on Aug. 30.

“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’s statement reads. “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 [tournament director] 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 US Open.”

Sinner’s announcement comes five days after the ATP’s No. 2 men’s player, Carlos Alcaraz, also withdrew from the Cincinnati Open. Alcaraz has been sidelined with a wrist injury since April, with the 23-year-old having missed the French Open and Wimbledon this year.