Novak Djokovic, of Serbia, serves to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, reacts after defeating Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alejandro Davidovich Fokina, left, of Spain, speaks with Novak Djokovic, of Serbia, after losing to Djokovic in the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, cools off during a third round men's tennis match against Alejandro Davidovich Fokina, of Spain, at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alejandro Davidovich Fokina, of Spain, wears mismatched socks as he serves to Novak Djokovic, of Serbia, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, reaches down to touch the court after defeating Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alejandro Davidovich Fokina, of Spain, reacts during a third round men's tennis match against Novak Djokovic, of Serbia, at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Novak Djokovic, of Serbia, returns to Alejandro Davidovich Fokina, of Spain, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alejandro Davidovich Fokina, of Spain, serves to Novak Djokovic, of Serbia, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Alejandro Davidovich Fokina, of Spain, serves to Novak Djokovic, of Serbia, during the third round of the men's tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)