Hingis, the world's top-ranked player, started her preparation for the U.S. Open with a 6-2, 7-6 (2) victory over Belgium's Dominique Van Roost on Tuesday in the second round of the $535,000 Acura Classic.

It was Hingis' first match since losing to Venus Williams in the quarterfinals at Wimbledon nearly a month ago.

``Overall, I think it was a good match to have,'' Hingis said. ``I still need a little bit of improvement on some of the strokes. Some parts of my game I got better and took some more risks.''

Also Tuesday, Anna Kournikova of Russia hit with authority and took advantage of numerous mistakes in an impressive 6-2, 6-3 first-round victory over Alexandra Stevenson.

Kournikova, who faces second-ranked Lindsay Davenport in the second round on Wednesday, never allowed the hard-hitting Stevenson to get into a groove.

``I had a good rhythm,'' said Kournikova, who reached the semifinals last week at the Bank of the West Classic.

``It's tough to get into a rhythm with Alexandra because you never know what's going to come,'' she added. ``It's either the fence or a winner or an ace or a double-fault.''

Stevenson held a 3-1 lead in the second set, but began spraying the ball all over the court. Kournikova broke Stevenson in two straight service games before winning when Stevenson, fittingly, hit a forehand long.

Hingis breezed through the first set against Van Roost then had to fight through a tough second set. The 19-year-old from Switzerland survived a break on her service in the 11th game as Van Roost took a 6-5 lead. But Van Roost managed just one point on her service game and Hingis broke back to force the tiebreak.

After holding her serve for a 2-1 lead, Van Roost committed four unforced errors and a double-fault to seal the match.

``I should have closed it out (sooner),'' said Hingis, who drew a first-round bye. ``I wasn't able to step it up.''

Seventh-seeded Anke Huber of Germany become the tournament's first upset victim when she lost 6-0, 7-6 (3) to Amy Frazier.

Frazier won the first nine games before Huber rebounded to make it close in the second set.

``It was going too smoothly,'' Frazier said. ``I knew there was no way it was going to stay like that for three sets.''

Down 3-0 in the second, Huber won three straight games. Huber, ranked ninth in the world, fought off two match points on Frazier's serve in the 10th game. Huber won the game, which lasted 16 points, and tied the score at 5-5 on her fourth break point of the game.

After each player held serve, Frazier took control of the tiebreak by winning the final four points.

Frazier's victory was her third this season over Huber.

In other matches Tuesday, fifth-seeded Conchita Martinez of Spain beat Kim Clijsters of Belgium 6-3, 6-4; sixth-seeded Nathalie Tauziat of France defeated Anne Kremer of Luxembourg 6-4, 6-3; eighth-seeded Sandrine Testud of France defeated Chanda Rubin 3-6, 7-5, 6-2; and Amanda Coetzer of South Africa beat Lisa Raymond 4-6, 7-5, 6-1.

Hingis, winner of five Grand Slam titles, is looking for her first major victory since capturing the 1999 Australian Open. She has been shut out of the last six Grand Slam championships.

Her preparation for the U.S. Open, which begins Aug. 28, includes playing next week at Los Angeles and then at Montreal. But Hingis' schedule does not include the Olympics, which start in Sydney just over a week after the Open ends.

``Last year, I was totally worn out (after the Open),'' she said. ``I didn't want to do the same thing and to make it worse. My health has been the most important to me.''