Melbourne  - Former great Patrick Rafter has voiced his doubts about the desire of deposed Australian Open winner Novak Djokovic after the Serb's retirement during his quarter-final with Andy Roddick.

During a television match commentary, the double US Open champion and one of the most popular of the former Aussie players, had his say about the increasingly controversial Djokovic.

Rafter said that the 21-year-old had a history of "pulling the pin" (with four retirements in Grand Slam matches).