First place male tennis player Novak Djokovic was forced to retire at the US Open on Sunday After hitting a line judge with the ball.

The three-time tournament champion accidentally provoked the referee during the fourth round match against Pablo Carreo Busta. Djokovic was 5-6 after falling while changing directions to follow the ball thrown by his opponent. Djokovic returned only to lose the game.

According to the tournament’s website, he seems to have hit a ball in frustration.

The photo and video showed Djokovic running to the woman’s aid after she appeared to have a sore throat or shoulder.

The The United States Tennis Association, the governing body of tennis in the United States, has issued a statement. “Follow his steps on the court intentionally hitting a ball dangerously or carelessly … carelessly ignoring the consequences.”

All ranking points earned in the tournament will be lost and fined for the prize money won at the US Open. The USTA said Djokovic would face additional fines.

Djokovic won first place in the men’s tournament. His unqualified Sunday ensured he would become the first Grand Slam champion in the US Open men’s singles.

The Serbian champion has previously won the tournament in 2011, 2015 and 2018. He has won multiple Grand Slam singles titles, the third best in male player history, and has won the Australian Open, French Open and Wimbledon.

Ahead of the US Open, Djokovic resigned from the Association of Tennis Professional Players’ Council. He promoted the proposed Professional Tennis Players’ Association, a joint union of male and female players.

He spoke to sports luminaries Serena Williams and Sloane Stephens about the effort. According to Sky Sports Saturday.

“I think we can all live together in the same environment,” Djokovic said. “It is very important that tennis players, who are part of the global sport, have only 100 per cent representation.”