Alexander Zverev, of Germany, serves to Andrey Rublev, of Russia, during the men's single final of the Western & Southern Open tennis tournament, Sunday, Aug. 22, 2021, in Mason, Ohio. (AP Photo/Darron Cummings)

Alexander Zverev, of Germany, holds the trophy after defeating Andrey Rublev, of Russia, in the men's single final of the Western & Southern Open tennis tournament, Sunday, Aug. 22, 2021, in Mason, Ohio. (AP Photo/Darron Cummings)

Alexander Zverev, of Germany, returns a shot to Andrey Rublev, of Russia, during the men's single final of the Western & Southern Open tennis tournament, Sunday, Aug. 22, 2021, in Mason, Ohio. (AP Photo/Darron Cummings)

Andrey Rublev, of Russia, returns to Alexander Zverev, of Germany, during the men's single final of the Western & Southern Open tennis tournament Sunday, Aug. 22, 2021, in Mason, Ohio. (AP Photo/Aaron Doster)

FILE - Alexander Zverev, of Germany, serves to Andrey Rublev, of Russia, during the men's single final of the Western & Southern Open tennis tournament in Mason, Ohio, in this Sunday, Aug. 22, 2021, file photo. Zverev is seeded for the U.S. Open, the year's last Grand Slam tennis tournament. Play in the main draw begins in New York on Monday, Aug. 30. (AP Photo/Aaron Doster, File)