( AFP )- A rattled Roger Federer was given a major scare in a five-set epic at the Australian Open Saturday, but he avoided the fate of number two seed Svetlana Kuznetsova who skidded out of the tournament.
Other casualties included women's sixth seed Anna Chakvetadze and men's seventh seed Fernando Gonzalez. Both were shown the exit just hours after the bad-tempered ousting of sixth seed Andy Roddick .
But six-time Grand Slam champion Venus Williams continued her steady progress with a 7-6 (7-0), 6-4 win over India's top player Sania Mirza .
And Australia's Lleyton Hewitt recovered from a set down to beat Cypriot Marcos Baghdatis 4-6, 7-5, 7-5, 6-7 (4/7), 6-3. The match ended at 4.33am Sunday, the latest finish to a singles match in Grand Slam history.
Federer , the Swiss defending champion, was stretched to the limit by courageous Janko Tipsarevic before downing the 49th ranked Serb 6-7 (5/7), 7-6 (7/1), 5-7, 6-1, 10-8 after four hours and 27 minutes.
The mammoth victory set him up with a fourth round encounter against either Argentine 21st seed Juan Monaco or 13th Czech seed Tomas Berdych on Sunday, and kept the top seed on course for his 13th Grand Slam title.
But it was a mighty struggle for the Swiss, who dropped sets for the first time in this year's tournament after becoming the only man since Bjorn Borg at the 1980 French Open to win a slam title without dropping a set here last year.
"What a great battle it was and it's a pity someone has to win in tennis sometimes," said Federer .
"I thought I was in great shape winning the fourth set but he served great and played some fantastic shots and in the end I tried to block out all the chances I had missed in the earlier sets.
"He came up with some fantastic plays and what a great victory it was for me."
The defeat of Kuznetsova , a former US Open champion, by Polish teenager Agneiszka Radwanska was the biggest upset yet among the women, with three of the top 10 seeds now gone by the third round.
Three top men's seeds have fallen -- ninth seed Andy Murray, Gonzalez, and Roddick , who was dumped in the early hours of Saturday by Germany's Philipp Kohlschreiber .
Eighteen-year-old Radwanska , ranked 28 in the world, said she was on a mission to avenge three losses to Kuznetsova last year, and fulfilled her orders, 6-3, 6 -4.
"I played against her a few times, always losing, so I said 'no more' . " It's very exciting, I'm very happy," said Radwanska , who has a fourth round match against either Russians Nadia Petrova or Ekaterina Makarova .
A devastated Kuznetsova blamed herself for blowing her chances.
"For me, it wasn't about her game. She played well, but I was not doing anything to win the match. And playing like this, I think I deserve to lose today," said the second seed.
With play on outside courts cancelled due to rain without a ball being struck, the action was restricted to the Rod Laver and Vodafone Arenas, which have retractable roofs.
On Rod Laver, Chakvetadze let slip a one set lead against 27th seeded Russian Maria Kirilenko , crashing 6-7 (6/8), 6-1, 6-2.
"It was a really tough match, in the first set I was a little bit unlucky and I decided to tell myself 'Maria, come on, keep working, fight for every point' and I did it and I'm so happy," said Kirilenko .
Chile's Gonzalez was last year's finalist, losing to Federer , but failed to produce the form that took him there on Saturday, slumping to Croatia's Marin Cilic , 6-2, 6-7 (4/7), 6-3, 6-1.
James Blake, seeded 12, fought back to rein in French veteran Sebastien Grosjean 4-6, 2-6, 6-0, 7-6 (7/5), 6-2 in what the American described as his greatest ever comeback.
Meanwhile, third seeded Serb Novak Djokovic breezed past unseeded American Sam Querrey 6-3, 6-1, 6-3 while women's fourth seed Ana Ivanovic swept into the final 16 by beating Slovenian Katarina Srebotnik 6-3, 6-4.
Djokovic now plays Hewitt, the 19th seed, for a place in the quarter-finals.