The top-seeded Dane struggled to keep her own game together in the 2 hour 24 minute match against Petkovic, squandering three set points in the opening set.

Petkovic took advantage of Wozniacki's failing forehand throughout the match regularly hitting to that side, to which a clearly frustrated Wozniacki had no control over at crucial points.

Top seed Wozniacki dug deep to take the second set and force a decider but Petkovic was not to be outdone and confidently served out the match to love, winning 7-5 3-6 6-3.

"Most of the players think they can overpower Caroline. I think that's the wrong approach, because that's where she's most comfortable, when she can run and bring the most balls back," Petkovic said after the match.

"What I try to do is mix it up and to make her play, and then when I had the short ball to go for it."

Elsewhere, third seed Vera Zvonareva of Russia defeated recent Indian Well's finalist Marion Bartoli of France 2-6 6-3 6-2.

Serbian Jelena Jankovic defeated Anabel Medina Garrigues of Spain 6-1 6-3.

Second seed Kim Clijsters's match with Serbian Ana Ivanovic was postponed to Tuesday due to heavy rain.