Updated

By Julian Linden

MELBOURNE (Reuters) - Kim Clijsters's fairytale return to grand slam tennis came to a shuddering halt at the Australian Open on Friday just as Justine Henin's own comeback started to gather momentum.

Clijsters was dumped from the first grand slam of the year after losing 6-0 6-1 to Russia's Nadia Petrova. The result was shocking enough but the scoreline defied all expectations, coming just four months after the Belgian won the U.S. Open.

Statistics can sometimes be misleading but the numbers in this match accurately summed up the thrashing. Clijsters won just five points in the first set and 17 in total. It was all over in 52 minutes.

"She was good but I made all the mistakes and she didn't have to do that much. It just sucks it has to happen at this stage of this tournament," Clijsters told reporters.

"This is something probably you want to forget as soon as possible and go home."

No one was more surprised by Clijsters's meek performance than Petrova. "I was preparing myself for a long day and a long match," she said. "It might have been a three setter."

Clijsters's loss overshadowed a special milestone by her compatriot and long-time rival Henin, who beat Russia's Alisa Kleybanova 3-6 6-4 6-2, marking her 500th career win.

Henin would have reached her landmark a lot earlier if she had not decided to suddenly quit the sport in 2008 when she was the number one player in the world.

"It's a big challenge to come back and I think I love challenges. That's the way I am," Henin said.

"I need always to push myself and to push the limits back. I'm very proud of what I'm doing right now."

EXPECTED RESULTS

Juan Martin del Potro, Andy Murray and Andy Roddick all won their matches with comparative ease but Rafa Nadal needed three and a half hours to beat dogged German Philipp Kohlschreiber.

The defending champion eventually won 6-4 6-2 2-6 7-5 and meets Croatia's Ivo Karlovic in the fourth round.

U.S. Open champion Del Potro showed no lingering effects of his five-set second round win over James Blake during his 6-3 0-6 6-4 7-5 win over German Florian Mayer.

Roddick recovered from a set down to defeat Spain's Feliciano Lopez 6-7 6-4 6-4 7-6. The American will next play Fernando Gonzalez of Chile after the 2007 Australian Open runner-up outlasted Evgeny Korolev 6-7 6-3 1-6 6-3 6-4.

Murray overcame a minor injury scare and more questions about his serve to beat Florent Serra of France 7-5 6-1 6-4 and is the only man through to the round of 16 who has not dropped a set.

"I don't think my serve is an issue at all," the Scotsman said. "Everyone is panicking about my serve."

Murray's next opponent is John Isner, the 2.06 meter American, whose main weapon is not hard to guess.

He thumped 26 aces past Gael Monfils in his 6-1 4-6 7-6 7-6 win over the Frenchman to lift his total for the championship to 81.

Henin's win over Kleybanova was not her best performance at Melbourne Park this week but enough to thrust her into the fourth round against Yanina Wickmayer, ensuring Belgium will have a quarter-finalist.

Her next opponent could provide some of the answers. Wickmayer sealed her place in the fourth round with a 6-1 6-7 6-3 win against Italy's Sara Errani and will give Henin a stern test.

UNDER SUSPENSION

Wickmayer made the U.S. Open semi-finals last year and is ranked 16 in the world but was forced to come through qualifying because she was under suspension when the registrations for the Australian Open closed.

Dinara Safina and Maria Kirilenko will play each other in one of two all-Russian fourth-round clashes on Sunday.

Safina defeated Britain's Elena Baltacha 6-1 6-2 in less than an hour and is slipping through the draw almost unnoticed even though she made the final last year and is ranked number two in the world.

Kirilenko matched her best performance at a grand slam when she defeated Italy's Roberta Vinci 7-5 7-6, showing that her first round win over Maria Sharapova was no fluke.

French Open champion Svetlana Kuznetsova needed all her big match experience to dig herself out of trouble and beat German qualifier Angelique Kerber 3-6 7-5 6-4. She will play her compatriot Petrova.

(Editing by Alison Wildey)