PARIS, May 30- Second seed Venus Williams crashed to Russia's Nadia Petrova in the fourth round of the French Open on Sunday, as Justine Henin edged a tight battle with Maria Sharapova.
Williams, a runner-up here in 2002, became the biggest casualty of the tournament so far when she lost 6-3, 6-4 to Petrova, the 19th seed, on Court Philippe Chatrier.
The American spurned two break points in the first set and Petrova made her pay for her profligacy by converting one of the two break points that came her way to take a one-set lead.
A netted forehand from Petrova, twice a semi-finalist, gave Williams an early break of serve in the second set but the Russian broke back and then broke again to take a 4-3 lead.
The Russian was 5-3 and 30-0 up on Williams’s serve when she appeared to lose her nerve, miscuing a straightforward smash and netting a forehand, but she recovered to whip a forehand past the American on her first match point.
She will meet compatriot Elena Dementieva, the fifth seed, for a place in the semi-finals.
Henin displayed all her trademark grit to see off fellow former world number one Sharapova 6-2, 3-6, 6-3 to reach the fourth round, hitting back from 0-2 and 0-40 down in the last set to claim victory.
The Belgian 22nd seed will play Australian seventh seed Samantha Stosur for a last-four berth.
The match resumed on Sunday after play was suspended at one set all amid fading light on Saturday evening.
Russian superstar Sharapova, the 23-year-old 12th seed, broke quickly to open up a 2-0 lead and then brought up four break points on Henin’s serve.
But the 27-year-old Henin, playing at Roland Garros for the first time since she last won the event in 2007 after coming out of retirement, battled back to level before clinching the decisive break of serve in the eighth game.
She secured victory on her second match point when Sharapova sent a backhand wide, as the Russian sank to her earliest French Open exit since 2003.
"Maria is a champion. You can’t give her any opportunities. I am happy to get through," said Henin after recording her seventh win in 10 meetings with the Russian.
"It was a real good test. The journey continues and I’m pleased to have a chance to win here at Roland Garros."
Sharapova admitted the third game of the deciding set had been crucial.
"I had opportunities but it was frustrating not taking them," said the Russian star.
"I was a little too hesitant, but I know the things I need to do and I just want to get back on the court and work on them. At 40-0 in that third game, she did a great job of being solid and served her way out of it."
Earlier, Dementieva swept into the quarter-finals with an emphatic 6-1, 6-3 victory over South African qualifier Chanelle Scheepers.
The Russian, who struggled to complete her third-round win over Aleksandra Wozniak due to a calf injury, won in 74 minutes to stay on course for a first Roland Garros final since she lost to Anastasia Myskina in the 2004 decider.
"After every match you lose, you’re always disappointed," said Scheepers, the first South African to reach round four since Amanda Coetzer in 1997.
"It was a really good experience for me, but obviously I wanted to do better."
Maria Kirilenko, the 30th seed who defeated defending champion Svetlana Kuznetsova in the previous round, failed in her attempt to follow her compatriot Dementieva into the last eight.
She lost 6-4, 6-4 to Italian 17th seed Francesca Schiavone, who will now take on either 14th-seeded countrywoman Flavia Pennetta or Danish third seed Caroline Wozniacki.