* Petrova too consistent for Venus
* Russian looking to reach third French Open semi-final
The American, a finalist in Paris in 2002, could not derail Petrova's consistent claycourt game on a windswept Centre Court as the Russian reached the quarter-finals for the first time since 2005.
"I had a day where I want to hit the ball crosscourt and it went down the line," a forlorn Venus told reporters.
Petrova, who saved three match points in the previous round against local hope Aravane Rezai, made up for an early break in the second set and wrapped up the win after one hour and 30 minutes.
She will next face fellow Russian Elena Dementieva, the fifth seed, for a place in the semi-finals.
Venus will stay in Paris a little longer as she is playing doubles with her younger sister, world number one Serena, before heading to the grass courts.
"At this point, I just have to do my best in doubles and then just play Wimbledon," she told reporters, adding she would not want to change her game.
"I'm not really thinking about reassessing my game at the moment," she said.
"She (Petrova) just seemed to play a little bit more consistently. I don't think she did anything super special."
For Petrova it was a first victory over the American in five attempts, and after the drama of seeing off Rezai in a match spread over two days due to rain the Russian was delighted to have fought her way through.
"It's my most dramatic French Open," Petrova, who reached the last four here in 2003 and 2005, told a courtside interviewer.
"Before yesterday's match I did not sleep all night. I'm very happy I came back strong on that Centre Court. I'm in very good condition physically."
Petrova has a 7-7 record against Dementieva.
(Editing by Miles Evans; To query or comment on this story email firstname.lastname@example.org)