Defending champion Amelie Mauresmo and third seed Svetlana Kuznetsova were bundled out of the Australian Open on Sunday by unheralded opponents, as the quarter-final line-up took shape.
Unseeded Lucie Safarova scored a shock 6-4, 6-3 win over second seed Mauresmo to reach a Grand Slam last eight for the first time while Israel's Shahar Peer dumped 2004 US Open champion Kuznetsova 6-4, 6-2.
Mauresmo's loss again raised questions of her being a choker.
The second seeded Frenchwoman appeared to have shaken off the tag last year when she won here and then at Wimbledon but her defence ended meekly against an opponent ranked 70 in the world.
"It's amazing, I still can't believe it, it's incredible," said Safarova, whose boyfriend Tomas Berdych simultaneously hit the winning shot in his third round victory over Dmitry Tursunov on an outside court.
"It was the first time I played on the Rod Laver Arena and when I was warming up in the morning I was saying 'wow, this is a big court'.
"But I felt really comfortable here with the crowd and everything, I'm really happy."
Safarova will play either seventh seed Elena Dementieva of Russia or Czech 10th seed Nicole Vaidisova in the quarters.
Mauresmo looked lethargic and rattled against a hungry Czech oppenent, with her serve misfiring and shots spraying wide.
Peer, 19, was overjoyed at one of the biggest victories of her career.
"I have nothing to lose and every match is open," said the 16th seed, who will now play either seven-time Grand Slam champion Serena Williams or 11th seed Jelena Jankovic in the first Grand Slam quarter-final of her career.
Men's defending champion Roger Federer goes for his 33rd consecutive win and a place in the quarters against the dangerous Novak Djokovic of Serbia, the youngest left in the men's draw at 19.
Federer has identified him as a player of the future and he has a glorious chance to prove his credentials against the best in the business on centre court.
"I beat Djokovic twice last year in the Davis Cup and at Monaco. He's definitely improved since," said Federer,
"He's came through his rounds fairly comfortably. Seems like he is playing pretty good. It's a dangerous match for me, that's for sure."
American sixth seed Andy Roddick vies for a place in the last eight against ninth seed Mario Ancic of Croatia.
Unseeded American Mardy Fish was the first man into the quarters, beating Spanish 16th seed David Ferrer and will play the winner of the Roddick-Ancic match.
In third round matches delayed from Saturday by rain, Chinese hope Li Na upset Marat Safin's sister Dinara Safina 6-2, 6-2 to set up an enticing clash with triple champion Martina Hingis.
The ice-cool Li, seeded 19, dominated the game against the Russian ninth seed with a booming serve and powerful forehand to continue a run of form that saw her make the semi-final of the Sydney International earlier this month.
Anna Chakvetadze of Russia also made the fourth round, beating unseeded Croat Jelena Kostanic Tosic 6-4, 6-4 and will play Swiss eighth seed Patty Schnyder for a place in the quarter-finals.
Slovak Daniela Hantuchova beat American Ashley Harkleroad 6-7 (6-8), 7-5, 6-3 and will now play in-form fourth seed Kim Clijsters.