Melbourne:
France's Jo-Wilfried Tsonga gained a measure of revenge for his defeat in the 2008 Australian Open final by beating an ailing Novak Djokovic in their quarter-final on Wednesday.
The 10th seed, beaten by the Serbian in four sets in the 2008 decider, came from a set down to win a thrilling encounter 7-6 (10/8), 6-7 (5/7), 1-6, 6-3, 6-1.
He earned a semi-final berth on Friday against world number one Roger Federer, who also came from a set down in beating Russian sixth seed Nikolay Davydenko, 2-6, 6-3, 6-0, 7-5.
It was Tsonga's second five-set win in as many matches, having prevailed over Spain's Nicolas Almagro 9-7 in the fifth set in the fourth round.
Before that win, Tsonga had never played a five-set match.
Djokovic, who had won his previous five matches against top-10 opponents, had all the momentum when he breezed through the third set, with Tsonga looking to have no answer to the depth of his groundstrokes.
Bearing a striking physical resemblance to former champion boxed Muhammad Ali, Tsonga found a way to climb off the canvas as Djokovic started to feel the effects of a taxing battle.
Tsonga said he noticed Djokovic was feeling unwell early in the fourth set.
"I was in good shape," Tsonga said.
"Maybe a little bit better (shape) than him.
"But he played unbelievable in the third set and I have seen him feel like that before and win."
Tsonga revived his chances with an early break in the third, immediately after which Djokovic called a medical time-out due to an upset stomach, apparently vomiting while in the locker room.
The Serbian retired from his quarter-final against American Andy Roddick last year due to cramping and heat illness.
He looked off his game when he returned as Tsonga skipped to a 5-0 lead on his way to leveling the match, despite a Djokovic rally late in the set.
Tsonga then gained a break in the first game of the final set and could have taken an iron grip on the match had he converted more break points in the third game.
However, a Djokovic double fault in the fifth game handed the Frenchman a 4-1 lead and he tightened his grip to make it five wins from seven clashes with the Serbian.
Despite successive marathons, Tsonga said he was ready to face Federer.
"I will be ready," he said. "It's going to be tough though, he's the best player ever."