Jessica Pegula, of the United States, left, greets Barbora Krejcikova, of the Czech Republic, after winning their quarterfinal match of the US Open tennis championships in New York.

Jessica Pegula, of the United States, reacts after defeating Barbora Krejcikova, of the Czech Republic, during the quarterfinal round of the US Open tennis championships in New York.

Barbora Krejcikova, of the Czech Republic, reacts after losing a point to Jessica Pegula, of the United States, during the quarterfinal round of the US Open tennis championships in New York.

Jessica Pegula, of the United States, returns a shot to Barbora Krejcikova, of the Czech Republic, during the quarterfinal round of the US Open tennis championships in New York.

Barbora Krejcikova, of the Czech Republic, returns a shot to Jessica Pegula, of the United States, during the quarterfinal round of the US Open tennis championships in New York.

Jessica Pegula, of the United States, returns a shot to Barbora Krejcikova, of the Czech Republic, during the quarterfinal round of the US Open tennis championships in New York.

Barbora Krejcikova, of the Czech Republic, returns a shot to Jessica Pegula, of the United States, during the quarterfinal round of the US Open tennis championships in New York.

Barbora Krejcikova, of the Czech Republic, returns a shot to Jessica Pegula, of the United States, during the quarterfinal round of the US Open tennis championships in New York.

Jessica Pegula, of the United States, serves to Barbora Krejcikova, of the Czech Republic, during the quarterfinal round of the US Open tennis championships in New York.

Barbora Krejcikova, of the Czech Republic, returns a shot to Jessica Pegula, of the United States, during the quarterfinal round of the US Open tennis championships in New York.