Kristina Mladenovic, of France, serves to Haley Baptiste, of the United States, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

A member of the USTA crew watches a match during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Coco Gauff, of the United States, returns a shot to Anastasija Sevastova, of Latvia, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Karolina Pliskova, of the Czech Republic, right, returns a shot to Anhelina Kalinina, of the Ukraine, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Karolina Pliskova, of the Czech Republic, serves to Anhelina Kalinina, of the Ukraine, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Borna Coric, of Croatia, returns to David Goffin, of Belgium, at the Western & Southern Open tennis tournament, Sunday, Aug. 23, 2020, in New York. (AP Photo/Frank Franklin II)

Alexander Zverev, of Germany, returns a shot to Kevin Anderson, of South Africa, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Novak Djokovic, of Serbia, reacts after a winning a set against Damir Dzumhur, of Bosnia and Herzegovina, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Naomi Osaka, of Japan, above, greets Misaki Doi, of Japan, at the net after defeating her during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Kevin Anderson, of South Africa, serves to Alexander Zverev, of Germany, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)

Angelique Kerber, of Germany, returns a shot to Ajla Tomljanovic, of Australia, during the first round of the US Open tennis championships, Monday, Aug. 31, 2020, in New York. (AP Photo/Frank Franklin II)