Seven-time Grand Slam champion Serena Williams staged another amazing comeback to down Israeli 16th seed Shahar Peer 3-6, 6-2, 8-6 on Tuesday and reach the Australian Open semi-finals.
The epic two-and-a-half hour victory means Williams, who won here in 2003 and 2005, will meet Czech 10th seed Nicole Vaidisova next.
"I am the ultimate competitor," Williams declared after wearing down her gritty 19-year-old opponent.
Williams, who went down a set for the second time in the tournament and came within two points of bowing out, said she fought hard to keep her comeback from injury on track.
"I wasn't playing my best tennis, I'm excited I was able to come through, I wasn't the best I can be today," said Willlams, who is ranked 81 in the world and unseeded here after a long injury lay-off.
While she flirted with disaster, her fighting qualities finally saw her through against Peer, who had her chance to serve out the match in the third set but failed to land a killer blow.
The Israeli, cheered on by a small but vocal group of supporters in her first Grand Slam quarter-final, stunned Williams with a service break in the second game.
She skipped away to a 3-0 lead as Williams allowed her mind to wander.
The former champion finally roused herself at 4-1 down after asking match officials to bring her a fresh pair of shoes at the changeover, slapping herself on the thigh and muttering to herself.
But it was too late to save the set, which the Israeli finally claimed in 41 minutes.
Written off by pundits as out-of-shape before the tournament, Williams was breathing hard in the Melbourne heat as she struggled to keep up with the ultra-fit Peer, who fulfils her mandatory military service with the Israeli army when not on the tennis tour.
Snarling and screaming herself on after hitting a succession of big winners, Williams pulled her game together as Peer's became more ragged, conceding two breaks as her serve lost its accuracy.
Williams, who easily beat Peer in their only previous meeting, threatened to overwhelm the Israeli as she ran away with the second set 6-2 in 30 minutes.
The third set looked to be going the same way as Peer squandered three break points and the experienced Williams made the most of her opportunities to pull ahead 4-1.
But Peer showed her own resilience, breaking back to win three games in a row to level the set at 4-4.
She pressured Williams again but the American blasted down two aces as she defended three break points.
Undaunted, Peer pressed again and got a break to take the set to 6-5 and gain the chance to serve out the match but Williams broke back, gesturing to her heart as she hit the winner.
Williams then finished off her plucky opponent to complete a win that provided great theatre but will leave the sole American woman left in the draw with a lot of recovering to do before she faces Vaidisova.