Jannik Sinner, the world’s No. 1 men’s tennis player, has withdrawn from the Cincinnati Open because of a knee injury. He still hasn't competed since capturing his second straight Wimbledon title last month. Sinner also withdrew from the tournament in Toronto that began Wednesday. The 24-year-old Italian has five Grand Slam titles and just needs to win the French Open to complete the career Grand Slam. Sinner’s announcement follows a similar decision by Carlos Alcaraz, who said Tuesday he also was withdrawing from the Cincinnati event because of a lingering wrist injury. It serves as an important warmup for the U.S. Open.