World number and top seed Novak Djokovic is sensationally disqualified from the US Open after striking a lines official with a ball during his last-16 match. The three time champion went 5-6 down in the first set to Spain's Pablo Carreno Busta when he hit a ball in the direction of the female official. The ball struck her in the throat and she could be heard gasping. Djokovic rushed over to check that she was okay and after a few minutes she got up and walked off the court. After the incident a lengthy discussion took place among the tournament referee and the umpire declared that Carreno Busta had won by default. Djokovic shook hands with Carreno Busta before leaving the court. Novak Djokovic's exit also means there will be a new male Grand Slam champion for the first time since Marin Cilic won at Flushing Meadows in 2014.