Melbourne - Andy Roddick beat the heat as he ended the Australian Open title defence of Novak Djokovic with the Serbian retiring to hand over a 6-7, (3-7), 6-4, 6-2, 2-1 victory in their Tuesday quarter-final.

The pair played in 31 degree Celsius temperatures on the first day of a Melbourne heat wave which was predicted to bring on temperatures 10 degrees warmer by Wednesday.

The retirement after two hours, 29 minutes was the fourth at a Grand Slam for the delicate Djokovic.

The second seed also failed to finish last summer in the Wimbledon semi-finals against Rafael Nadal, and twice at Roland Garros - a 2006 quarter-final against Nadal and the second round a year earlier against Guillermo Coria.

The Serb crashed to 39 unforced errors as the strength ebbed from his game.

The 21-year-old needed two medical treatments on the sideline during the agonising contest, with trainers at one stage applying ice around his neck.

Roddick, who fired 16 aces, next plays the winner from second seed Roger Federer and Argentine Juan Del Potro. (dpa)