MOSCOW -- Martina Hingis was stunned by 169th-ranked Nadia Petrova 6-2, 6-2 Monday in the first round of the Kremlin Cup.

It was the first match for Hingis, who turned 22 Monday, since her fourth-round loss to Monica Seles at the U.S. Open. Hingis, formerly ranked No. 1 and a five-time Grand Slam singles champion, had ankle surgery in May and was sidelined three months.

In another upset, French Open champion Albert Costa was eliminated by Nicolas Escude 7-5, 3-6, 6-1. That was the only men's match of the day.

Against Petrova, the fifth-seeded Hingis' serve was broken in the first game and she dropped the final four games of the first set. Hingis wound up losing the match in just 49 minutes.

"I had certain problems with my service today, while Nadia was serving pretty well, preventing me from catching the rhythm of the game," Hingis said.

"It was my first indoor tournament after the injury and definitely not my best day."

Hingis won this tournament in 2000, and was the runner-up last year.

In other first-round action, Tatiana Panova beat Anne Kremer 7-5, 6-3, and two-time champion Magdalena Maleeva defeated Anna Smashnova 6-1, 6-2.

Costa, seeded third, had three set points while serving at 5-3 in the first set. But the 48th-ranked Escude erased those en route to taking four games in a row.

Escude raced to a 5-0 lead in the final set.