Czech Republic's Barbora Krejcikova serves to Zarina Diyas of Kazakhstan during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Czech Republic's Barbora Krejcikova returns to Zarina Diyas of Kazakhstan during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Zarina Diyas, of Kazakhstan, casts a shadow as she serves to Czech Republic's Barbora Krejcikova during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Czech Republic's Barbora Krejcikova returns to Zarina Diyas of Kazakhstan during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Czech Republic's Barbora Krejcikova returns to Zarina Diyas of Kazakhstan during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Television camera operators with Olympic Broadcasting Services film a tennis match between Czech Republic's Barbora Krejcikova and Zarina Diyas of Kazakhstan at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Czech Republic's Barbora Krejcikova serves to Zarina Diyas of Kazakhstan during the tennis competition at the 2020 Summer Olympics, Saturday, July 24, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)