Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Daniel Elahi Galan, of Colombia, serves to Alexander Zverev, of Germany, second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, serves to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, serves to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Daniel Elahi Galan, of Colombia, serves to Alexander Zverev, of Germany, second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alexander Zverev, of Germany, returns to Daniel Elahi Galan, of Colombia, during second round of the tennis competition at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)