Petrova struggled to get to grips with the clay surface

The 24-year-old Russian, who won three clay-court titles last season before injury saw her miss the French Open and Wimbledon, won 6-3 7-5.

"I was playing against two opponents," said world number nine Petrova. "One was on the other side of the net and one was on the same side as I was.

"I really had a difficult time because last week I didn't do much practising."

She added: "The previous week I played Fed Cup and that was indoors so it was completely different conditions."

Sixth seed Anna Chakvetadze also had to fight hard to book a spot in the second round.

The Russian overcame an inconsistent performance to beat American Jill Craybas 7-6 (8-6) 7-5.

But eighth seed Katarina Srebotnik was a first-round casualty, going down 6-3 4-6 6-1 to Alona Bondarenko of the Ukraine.

Defending champion Kim Clijsters, playing her only clay court tournament of her farewell season, is seeded second behind fellow Belgian Justine Henin.

Three-time runner-up Svetlana Kuznetsova of Russia is seeded three while 2004 champion Venus Williams is also playing but is unseeded.