STUTTGART, Germany — Gisela Dulko of Argentina upset fourth-seeded Victoria Azarenka of Belarus 6-4, 6-3 on Wednesday to reach the third round of the Porsche Grand Prix.

Azarenka came into the tournament as one of the hottest players on the tour, with three tournament titles, including the Miami Masters. But she ran into a player who is perhaps most comfortable on clay.

The Stuttgart tournament is the only event on the circuit to be played on indoor clay.

"I love it. No wind, no sun," Dulko said. "She won a lot of matches this year but I feel confident on clay. Everything worked for me. I was solid but I was also aggressive, especially on my serve. I just believed in myself, that I can beat top players."

Fifth-seeded Svetlana Kuznetsova of Russia beat German qualifier Andrea Petkovic 6-4, 5-7, 6-1 in the first round, while last year's runner-up Nadia Petrova beat Zheng Jie of China 6-4, 5-7, 6-4, and Daniela Hantuchova of Slovakia beat Alize Cornet of France 6-3, 6-1.

Kuznetsova wasted a match point in the second set against the 143rd-ranked Petkovic, who missed nearly the entire 2008 season with torn knee ligaments.

Kuznetsova then double-faulted to give Petkovic a break and a 6-5 lead in the second set, and the German clinched her set point with an ace. But the Russian bounced back and won the next five games before wrapping up the match.

"I didn't have the patience or the experience in the third set," Petkovic said.

Kuznetsova is a three-time semifinalist in Stuttgart, when it was still played on a hard indoor surface.

"I had too many ups and downs, especially in the second set," Kuznetsova said. "I am quite disappointed with myself."