Sharapova won a nail-biter 6-1 4-6 6-4 against her fellow Russian to set up a clash with Frenchwoman Marion Bartoli.
France’s 11th seed Bartoli upset fifth-seeded Czech Petra Kvitova 1-6 6-2 6-0.
Petrova led 2-0 in the third set when rain halted proceedings for an hour and 13 minutes.
Sharapova spoke to her father, Yuri, on the telephone during the break and took his advice to play with increased energy and aggression when play resumed. Petrova said it was Sharapova’s lucky day because she could regroup when the match was slipping away.
“You should ask her what happened,” a frustrated Petrova said. “I don’t know what went through her head. I had been in control in the third set. I had everything in my hands.
“Maria looked hesitant and she couldn’t get a hold of her game. But then after the rain break, actually it went in her favour because she had time to think, regroup, talk to her coach.
“And then she came out completely cool and collected. She started playing big tennis. Unfortunately, luck was on her side today.”
Sharapova paused and then shrugged when told of Petrova’s remarks. “Great,” Sharapova said. “I’m the winner so whatever she wants to call it is fine with me.”
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