World No.1 and top seed Novak Djokovic was defaulted from the US Open on Sunday after accidentally hitting a linesperson with a ball.
Djokovic was trailing Pablo Carreno Busta 5-6 in the first set of their fourth-round contest when frustration got the better of him.
After seeing three set points slip by at 5-4, Djokovic slipped over and required medical attention at 5-5 before dropping serve, prompting his angry reaction.
The USTA later released a statement citing the Grand Slam rulebook regarding a player “intentionally hitting a ball dangerously or recklessly within the court or hitting a ball with negligent disregard of the consequences”.
Djokovic then released his own statement, saying: "This whole situation has left me really sad and empty. I checked on the lines person and the tournament told me that thank God she is feeling ok.
“I’m extremely sorry to have caused her such stress. So unintended. So wrong."
The 33-year-old had been trying to win his fourth US Open and 18th Grand Slam title, and will now head to Europe for the Rome Masters followed by the French Open later this month.
Djokovic's exit in New York brings to an end a remarkable 29-match winning streak that stretched back to last November.
Carreno Busta, a former semifinalist at Flushing Meadows, goes on to face Canada's Denis Shapovalov in the quarterfinals.