Elena Rybakina, of Kazakhstan, returns to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Elena Rybakina, of Kazakhstan, serves to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Elena Rybakina, of Kazakhstan, returns to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Donna Vekic, of Croatia, serves to Elena Rybakina, of Kazakhstan, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Elena Rybakina, of Kazakhstan, returns to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Elena Rybakina, of Kazakhstan, serves to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Elena Rybakina, of Kazakhstan, returns to Donna Vekic, of Croatia, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)

Donna Vekic, of Croatia, returns to Elena Rybakina, of Kazakhstan, during the third round of the women's tennis competition at the 2020 Summer Olympics, Tuesday, July 27, 2021, in Tokyo, Japan. (AP Photo/Patrick Semansky)