World number one Jannik Sinner has pulled out of the Cincinnati Open with a right knee injury, tournament organisers said on Sunday, handing the Italian a blow in his preparations for this month's U.S. Open.The 24-year-old Italian, ‌who ⁠claimed his ⁠fifth Grand Slam title at Wimbledon last month, had also pulled out of the Canadian Open, a key warm-up event for the U.S. Open.Sinner won the Cincinnati title in 2024 and finished runner-up to seven-times Grand ​Slam champion Carlos Alcaraz there ⁠last year."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 in a statement."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... I can't wait to be back ​next year ​and I'm now ⁠focusing on getting ready for the U.S. Open."Sinner's withdrawal further depletes the field in Cincinnati, with U.S. Open ​champion Alcaraz also sidelined by a wrist injury.The Cincinnati Open main draw begins on August 13, while the U.S. Open main draw gets under way on August 30.