Former world No.1 Martina Hingis says she has exceeded her expectations by making the Australian Open quarter-finals in her return to grand slam tennis after an absence of more than three years.

Hingis defeated Australian Samantha Stosur in straight sets 6-1 7-6 (10-8) in their fourth round match at Melbourne Park and is yet to drop a set in her first grand slam event since 2002.

But, rather than weighing up how far she could progress in what has already been a dream comeback for her, Hingis said she was relishing making it this far.

"This is definitely one of the more relieving matches I've had," Hingis said.

"Now I already stand in the quarter-finals, making the last eight coming into this event I never would have thought I would get that far, but here I am.

"No-one can take that away from me, I'm really happy right now."

Having conceded just 10 games in her previous three matches combined, Monday night's match against Stosur was Hingis' toughest test in the tournament so far.

She twice failed to serve out the match in the second set and then needed four match points in the tiebreak to finally clinch it.

Hingis said nerves and tiredness affected her late in the match, and she would have to improve her concentration to have a chance in her quarter-final against second seed Kim Clijsters on Wednesday.

But she added she would approach that match without the burden of expectations she had felt when she was at the top of the tennis world.

"It was just always very stressful because you always had to defend yourself, you were No.1 and every match you went out there to win, but had so much to lose," she said.

"Right now I don't have anything to lose, I enjoy going out there and playing those matches.

"There's still definitely a lot on the spot for me but I probably take a different approach this time around for sure, I have nothing to prove any more."

While Hingis has played Clijsters five times, winning four of them, the last of those matches was more than four years ago and she said nothing could be drawn from them.

"Times have changed, it's so long ago and she's gone on with her game, I'm trying to get back on track, it will be a new story this time around," Hingis said.

"Probably a thing that's changed is that she's the favourite and I'm just the underdog now."

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