Melbourne, Jan. 27 : Defending champion Novak Djokovic has quit the Australian Open, retiring from his quarter-final against Andy Roddick on Tuesday.
Djokovic, the No. 3-seed, from Serbia, was trailing the No. 7 seed, from the United States, 6-7 (5-7) 6-4 6-2 2-1 when he quit the match, after two-and-a-half hours, apparently suffering from heat stress.