Coco Gauff, right, of the United States, shakes hands with Tatjana Maria, of Germany, during a second round match of the U.S. Open tennis championships in New York.

Coco Gauff, of the United States, returns a shot to Tatjana Maria, of Germany, during a second round match of the U.S. Open tennis championships in New York.

Tatjana Maria, of Germany, returns a shot to Coco Gauff, of the United States, during a second round match of the U.S. Open tennis championships in New York.

Coco Gauff, of the United States reacts against Tatjana Maria, of Germany, during a second round match of the U.S. Open tennis championships in New York.

Victoria Azarenka, of Belarus, reacts against Clara Burel, of France, during a second round match of the U.S. Open tennis championships in New York.

Clara Burel, of France, returns a shot to Victoria Azarenka, of Belarus, during a second round match of the U.S. Open tennis championships in New York.

Victoria Azarenka, of Belarus, returns a shot to Clara Burel, of France, during a second round match of the U.S. Open tennis championships in New York.

Clara Burel, of France, returns a shot to Victoria Azarenka, of Belarus, during a second round match of the U.S. Open tennis championships in New York.

Elina Svitolina, of Ukraine, serves to Angelina Kalinina, of Ukraine, during a second round match of the U.S. Open tennis championships in New York.

Angelina Kalinina, of Ukraine, returns a shot to Elina Svitolina, of Ukraine, during a second round match of the U.S. Open tennis championships in New York.

Elina Svitolina, of Ukraine, returns a shot to Angelina Kalinina, of Ukraine, during a second round match of the U.S. Open tennis championships in New York.