Melbourne: Defending champion Amelie Mauresmo was bundled out of theAustralian Open by an unheralded opponent, but Serena Williams and RogerFederer marched into the quarter-finals.

American sixth seed Andy Roddick also remains in the hunt, digging deep toovercome Mario Ancic in five sets to make the last eight where he will meetcompatriot Mardy Fish, who took care of 16th seeded Spaniard David Ferrer.

But third seed Svetlana Kuznetsova joined Mauresmo on the scrap heap,slumping to Israel'sShahar Peer 6-4, 6-2.

The manner of Mauresmo's 6-4, 6-3 loss to unseeded Lucie Safarova againraised questions of her being a choker.

The second seeded Frenchwoman appeared to have shaken off the tag last yearwhen she won here and then at Wimbledon buther defence ended meekly against an opponent ranked 70 in the world.

"I'm not completely down or whatever, I'm just disappointed," saidthe ousted title holder.

"But I am going to go back on the court, go back to work, that'sobviously what I need."

Safarova, who will now play Czech 10th seed Nicole Vaidisova, who beatseventh seed Elena Dementieva of Russia, said it was the biggest winof her career.

"It's amazing, I still can't believe it, it's incredible," shesaid.

Peer, 19, was overjoyed at one of the biggest victories of her career overthe 2004 US Open champion.

"I have nothing to lose and every match is open," said the 16thseed, who will now play seven-time Grand Slam champion Williams.

Williams rolled back the years to crush eleventh seed Jelena Jankovic 6-3,6-2, touted as one of the hottest new talents in tennis.

It was the sternest test yet for Williams, a winner here in 2003 and 2005,as she comes back from injury that restricted her to just four tournaments lastyear.

"It was absolutely sensational, you know I had a lot of fun out thereand I just enjoy Rod Laver Arena a lot and I play some of my best tennishere," she said.

"I like being a dangerous floater, it's fun," she said.

Defending champion and top seed Federer wrapped up his 33rd consecutive win,against the dangerous Novak Djokovic of Serbia6-2, 7-5, 6-3, and will next play Tommy Robredo of Spain as he bids for his 10th GrandSlam crown.

"I feel good physically. I've been winning in straight sets every time,plus a day off, and I couldn't be better," said the Swiss maestro, who haswon in Melbournetwice before and hasn't dropped a set this year.

Roddick ovecame the aggressive net-charging Ancic 6-3, 3-6, 6-1, 5-7, 6-4 injust over three hours with his greater consistency and patience the key tovictory.

"Win or lose I had to turn the tables on his aggression," Roddicksaid.

"I just put the ball in the court that helped. He missed a couple ofvolleys maybe he wouldn't normally miss."

In third round matches delayed from Saturday by rain, Chinese hope Li Naupset Marat Safin's sister Dinara Safina 6-2, 6-2 to set up an enticing clashwith triple champion Martina Hingis.

The ice-cool Li, seeded 19, dominated the game against the Russian ninthseed with a booming serve and powerful forehand to continue a run of form thatput her in the semi-final of the Sydney International earlier this month.

Anna Chakvetadze of Russiaalso 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 thequarter-finals.

Slovak Daniela Hantuchova defeated American Ashley Harkleroad 6-7 (6-8),7-5, 6-3 and will now play in-form fourth seed Kim Clijsters.