Alexander Zverev, of Germany, returns a shot against Jannik Sinner, of Italy, during the fourth round of the US Open tennis championships, Monday, Sept. 6, 2021, in New York. (AP Photo/Seth Wenig)

Alexander Zverev, of Germany, celebrates after winning his match against Jannik Sinner, of Italy, in the fourth round of the US Open tennis championships, Monday, Sept. 6, 2021, in New York. (AP Photo/Seth Wenig)