After his now infamous sledge at a first round opponent he accused of pulling a heart muscle, unheralded Aussie Nathan Healey showed his ticker was working just fine as he advanced to the third round of the Australian Open.

Battling heat stress and his body wracked with cramp, the 24-year-old from Gosford left absolutely nothing in the tank in overcoming American qualifier Amer Delic in four sets in sweltering heat for the biggest win of his tennis career.

Healey was forced to call a medical timeout when leading 4-3 in the fourth set - his legs iced by a trainer as the cramp set in.

He bravely closed the match out, nearly collapsed as he returned to the dressing rooms, then was forced to delay his post-match press conference until more than two hours after his 6-4 6-7 (4-7) 6-3 6-4 victory as he soaked in an ice bath to help recover.

"I hope I'm going to make some sense," said Healey as he walked into the media conference draped in a towel, still visibly shivering from his ice bath.

"I started to cramp at 4-2 in the fourth and I thought I was going to be in trouble there.

"Afterwards I walked into the change rooms and I nearly fell over.

"It sort of snuck up on me. I'm still shivering (from the ice bath) but I feel a lot better."

The dramatic aftermath should take nothing away from Healey's gritty performance in front of friends, family and loyal supporters at Melbourne Park.

Ranked No.240 in the world, Healey continued from where he left off in his first round victory over Italian Filippo Volandri, who quit with the Aussie two sets up.

Healey's only two previous wins in grand slam tournaments came in the opening rounds of the two most recent Australian Opens - both times benefitting from mid-match withdrawals by his opponents.

But he showed he can go the distance - guaranteeing himself his biggest ever pay day of at least $46,000 from his third round match against Russian No.5 seed Nikolay Davydenko on Saturday.

The bad news is another 35 degree day is forecast for what will be only Healey's fourth Grand Slam singles match, but he believes he is playing well enough to test the Russian and not just be cannon fodder.

"I'm confident, I'm feeling good out there and I'm learning so much with every game. If I can just remain on my feet, I'm in with a real shot," Healey said.

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