Three-time champion Novak Djokovic defaulted from US Open(1/4)

Novak Djokovic of Serbia checks a linesman after hitting her with a ball in reaction to losing a point to Pablo Carreno Busta, of Spain, during the fourth round of the US Open tennis championships at USTA Billie Jean King National Tennis Center, New York, U.S., Sept. 6, 2020. (Photo/Agencies)

Medical staff and Novak Djokovic of Serbia check on a line judge after she was hit in the throat by a ball hit by Djokovic after he lost a game to Pablo Carreno Busta of Spain in the first set on day seven of the 2020 U.S., New York, U.S., Sept. 6, 2020. (Photo/Agencies)

Novak Djokovic of Serbia and a tournament official tend to a linesperson who was struck with a ball by Djokovic against Pablo Carreno Busta of Spain on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center, New York, U.S., Sept. 6, 2020. (Photo/Agencies)

Novak Djokovic of Serbia leaves the court after being defaulted for striking a lines person with a ball against Pablo Carreno Busta of Spain on day seven of the 2020 U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center, New York, U.S., Sept. 6, 2020. (Photo/Agencies)