Melbourne - Swiss great Roger Federer believes four-time Grand Slam champion Kim Clijsters can achieve "a lot" on her comeback after seven years out of the game, insisting age doesn't matter.
The 36-year-old Belgian, who retired after the 2012 US Open, is set for a return in March, having originally scheduled her comeback at next week's Australian Open until a knee injury scuppered the plan.
Federer said he had not seen Clijsters swing a racquet in years but "knowing what she could do before, seeing her and her personality, if she is coming back, it's because she's really in the mood to".
"She wants to see what else is left to do," he added. "I think age doesn't matter, to be honest. I think it's the fitness and the mind that matters.
"So I think a lot is possible, even though there should be no expectations from her side and from anybody else."
Clijsters, affectionally known as 'Aussie Kim' in Australia due to her former relationship with Lleyton Hewitt, has won 41 titles, including three US Opens (2005, 2009 and 2010) and one Australian Open (2011).
She turned professional in 1997 and reached the world number one ranking for the first time in 2003, and most recently in February 2011.
"I think she's going to be fresh," Federer said.
"Does she have to play 30 tournaments a year? No, not really. She plays when she's in the mood to, when it suits her family. I think it's going to be very exciting to follow."