2009 US Open champion Juan Martin del Potro is sidelined for the Australian Open due to ongoing knee issues.
The unlucky Argentine is still striving to recover from a kneecap fracture suffered at Queen's Club last June. He joins Richard Gasquet - who is also dealing with a knee problem - Andy Murray, and Kei Nishikori in withdrawing from the men's singles event.
Del Potro, 31, reached the quarterfinals of the Australian Open in 2009 and 2012.
