Novak Djokovic has been disqualified from the US Open after striking a line judge with the ball.

The world No 1 who was trailing his opponent Pablo Carreno Busta 6-5 in the opening set of their fourth-round match, had just dropped his serve.

Out of frustration, he hit the ball behind him and it hit a female line judge. But he rushed and checked on her after she was hit and apparently hurt.

Tournament referee Soeren Friemel came out on to the court and spoke to chair umpire Aurelie Tourte and Andreas Egli, the Grand Slam supervisor, before a lengthy discussion between tournament officials and Djokovic.

He pleaded his case at length before accepting his fate, collecting his rackets and walking off the court.

Djokovic who will also be fined again for not attending his press conference, wrote a lengthy statement on instagram, apologizing for his behaviour at court.

“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. I’m not disclosing her name to respect her privacy.

“As for the disqualification, I need to go back within and work on my disappointment and turn this all into a lesson for my growth and evolution as a player and human being.

“I apologise to the @usopen tournament and everyone associated for my behaviour. I’m very grateful to my team and family for being my rock support, and my fans for always being there with me. Thank you and I’m so sorry.”

According to the Grand Slam rulebook, any player who dangerously or recklessly hits within the court without regard for the consequences, will lose ranking points earned in the tournament and will be fined the prize money won at the tournament in addition to any or all fines levied with respect to the offending incident.

Carreno Busta will now face a quarter-final against Denis Shapovalov after the Canadian produced a fine display to oust seventh seed David Goffin 6-7 (0-7) 6-3 6-4 6-3.

Djokovic’s disqualification now means that this will be the first time since Marin Cilic won the US Open title in 2014, a new man will become the Grand Slam champion.