Maria Sakkari, of Greece, hits a forehand to Karolina Pliskova, of the Czech Republic, during the quarterfinals of the U.S. Open tennis tournament Wednesday, Sept. 8, 2021, in New York. (AP Photo/Frank Franklin II)

Maria Sakkari, of Greece, reacts after winning the first set against Karolina Pliskova, of the Czech Republic, during the quarterfinals of the U.S. Open tennis tournament Wednesday, Sept. 8, 2021, in New York. (AP Photo/Frank Franklin II)

Karolina Pliskova, of the Czech Republic, reacts after missing a shot to Maria Sakkari, of Greece, during the quarterfinals of the U.S. Open tennis tournament Wednesday, Sept. 8, 2021, in New York. (AP Photo/Frank Franklin II)

Karolina Pliskova, of the Czech Republic, eyes her return to Maria Sakkari, of Greece, during the quarterfinals of the U.S. Open tennis tournament Wednesday, Sept. 8, 2021, in New York. (AP Photo/Frank Franklin II)