MELBOURNE, Australia -- U.S. Open champion Kim Clijsters slumped out of the season's first major in a shocking 6-0, 6-1 loss to No. 19-seeded Nadia Petrova on Thursday.
Clijsters, who won the U.S. Open in September in only her third tournament back from two years off to get married and have a baby, seemed distracted as she won only five points in an 18-minute first set in her third-round match Friday at the Australian Open.
It barely got better in the second set, when she held serve only once and managed to make it last 52 minutes, saving two match points.
The loss ends hopes of a Clijsters quarterfinal matchup with fellow comeback Belgian Justine Henin, who advanced to the fourth round earlier Friday with a three-set win over Alisa Kleybanova.
The magnitude of the defeat was more astonishing given that Clijsters had beaten Henin in a three-set final at an Australian Open tuneup event at the Brisbane International on Jan. 9.
The lopsided scoreline ranks among her worst. She only won four games in a 6-0, 6-4 loss to Henin in the 2003 French Open final. It was also her first loss in five matches against the 27-year-old Petrova.
Earlier in the day, Henin had staged another memorable comeback to advance in her first Grand Slam out of retirement with a 3-6, 6-4, 6-2 win over No. 27 Alisa Kleybanova.
Facing two break points at 1-3 in the second set, it seemed as if Henin's dramatic win over Olympic gold medalist and fifth-ranked Elena Dementieva on Wednesday had sapped too much energy. After all, that was only the seventh match for the seven-time Grand Slam winner since she returned from 20 months off the tour.
But Henin managed to hold that game, hitting the lines with her groundstrokes instead of just missing them, and in the next game converted her first break-point chance against Kleybanova. As soon Henin found her range, the match was as good as over.
"I kind of survived a little bit today," Henin said. "It's always good to win this kind of match because I came back from nowhere.
"Physically I suffered a little bit in the last two days, but finally I did it. I'm very happy that I have another chance to get better in the next round."
Henin, unranked and playing on a wild-card entry, had a momentary lapse in the deciding set when Kleybanova broke her serve, but otherwise dominated the last 10 games.
Only two nights earlier, Henin had to save set points to finish off Dementieva in a tiebreaker, drawing on the experience of losing in similar circumstances to Clijsters after holding match points in the Brisbane International final.
That was Henin's first tournament since she quit while holding the No. 1 ranking in May 2008. In what had shaped as a Belgian quarter, Henin set up a fourth-round against Yanina Wickmayer.
Wickmayer, who is ranked No. 16 but unseeded because she was under a suspension -- since overturned -- for breaching the World Anti-Doping Agency's "whereabouts rule" when direct entries closed for the Australian Open -- advanced 6-1, 6-7 (4), 6-3 over Sara Errani. She needed painkillers for back pain against Errani and said she'd need treatment before facing Henin.
Now the winner of that match will play Petrova.
In other matches, second-seeded Dinara Safina had a 6-1, 6-2 victory over Britain's Elena Baltacha and next will play fellow Russian Maria Kirilenko, who beat Italian Roberta Vinci 7-5, 7-6 (4). Kirilenko ousted 2008 champion Maria Sharapova in the opening round.
"I think Sharapova hits it harder than Safina, so I am prepared for sure," Kirilenko said.
Former No. 1 Jelena Jankovic was upset 6-2, 6-3 by No. 31 Alona Bondarenko, while China's Zheng Jie upset 2007 Wimbledon finalist Marion Bartoli of France 5-7, 6-3, 6-0.
On the men's side, U.S. Open champion Juan Martin del Potro had a 6-3, 0-6, 6-4, 7-5 win over Florian Mayer, then crossed himself, kissed his finger and reached for the sky.
"The crowd helped me a lot to give fight. I wanted to be alive a few more days here in Melbourne," said the 21-year-old Argentine, who is a reigning major champion for the first time.
Del Potro lost the Roger Federer in the quarterfinals here last year, but avenged that by beating the 15-time Grand Slam winner in the U.S. Open final in September.
Asked if he felt any different this time around, del Potro laughed, held open his arms and said: "I feel bigger!"
"My life hasn't changed too much," he said. "Of course, it's beautiful, you get up, see the trophy of the U.S. Open. But you want more."
If he wins in the fourth round, he could meet former No. 1-ranked Andy Roddick in the quarterfinals.
Seventh-seeded Roddick was challenged all the way in a 6-7 (4), 6-4, 6-4, 7-6 (3) win over Feliciano Lopez and will play 2007 runner-up Fernando Gonzalez of Chile, who was backed by a noisy Chilean contingent in stifling conditions on Showcourt 2 as he beat Kazakhstan's Evgeny Korolev 6-7 (5), 6-3, 1-6, 6-3, 6-4.
Britain's Andy Murray had a 7-5, 6-1, 6-4 win over Florent Serra of France and will now play American John Isner, who fired 26 aces and hit 73 winners in a 6-1, 4-6, 7-6 (4), 7-6 (5) victory over No. 12 Gael Monfils of France.
On paper, it was an upset, although 24-year-old Isner -- who was given the last seeding for the tournament after Frenchman Gilles Simon withdrew -- went into the match 2-1 against Monfils.
The winner of the Murray-Isner match is likely to face defending champion Rafael Nadal in the quarterfinals. Nadal had a night match Friday against Philipp Kohlschreiber of Germany.