Novak Djokovic is out of the 2016 Dubai Duty Free Tennis Championships after being forced to retire from his quarter-final against Feliciano Lopez. The world No1, a four time winner in Dubai, appeared to be suffering from an eye problem and duly quit after losing the first set to his Spanish opponent 6-3. Djokovic had initially called for the trainer while trailing 1-2. He then resumed play, but after making 18 unforced errors in his nine games, conceded the match to No6 seed Lopez. Afterwards, Lopez said Djokovic told him that he had an eye infection "since a few days already." The concession comes just a day after Djokovic became only the 12th player in the Open Era to register 700 career wins. It also means his extraordinary run of making 17 successive Tour finals comes to an end. In Friday's semi-finals Lopez will face Cypriot Marcos Baghdatis in the evening game (not before 7pm) while Nick Krygios will take on the second seed Stanislas Wawrinka (not before 5pm).