Ai Sugiyama took advantage of numerous unforced errors and played consistently to upset second-seeded Svetlana Kuznetsova 2-6, 6-4, 6-3 in the third round of the Acura Classic in Carlsbad, California.

Kuznetsova, ranked fourth in the world, committed 69 unforced errors, including 56 over the final two sets in her first match since losing in the Wimbledon quarterfinals more than a month ago.

``I think I was playing good tennis at times,'' said US Open champion Kuznetsova. ``I just didn't keep my level at the top.''

Kuznetsova became the last of six seeded Russian players to be eliminated from the US$1.3 million (HK$10 million) event.

Russia's only remaining player from the 11 who entered the event is unseeded Anna Chakvetadze, who defeated Elena Likhovtseva 6-3, 6-1.

Fifth-seeded Patty Schnyder of Switzerland is the highest-seeded player left after her 6-7 (1/7), 6-1, 6-4 win over number 17 Francesca Schiavone of Italy.

Tenth-ranked Kim Clijsters of Belgium is the only top-10 player remaining in the draw. Clijsters, seeded seventh, moved into the quarterfinals with a 6-1, 6-3 win over Jelena Jankovic of Serbia and Montenegro.

Clijsters is shooting for her fifth title this season.

Sixth-seeded Mary Pierce defeated fellow Frenchwoman Nathalie Dechy, 7-5, 6-3 in the featured night match.

Sesil Karatantcheva of Bulgaria advanced to her third quarterfinal this season with a 6-1, 6-2 win over Mashona Washington. Karatantcheva, who will turn 16 on Monday, eliminated the last American in the field.

Kuznetsova breezed through the first set before Sugiyama took a close second set. Games went to serve until Sugiyama broke through in the fifth to take a 3-2 lead and won her service game at love for a 4-2 advantage. Sugiyama closed out on her first match point when Kuznetsova hit a backhand into the net.

``I gave her a chance to get into the match in the second (game),'' Kuznetsova said. ``And in the third, it was much more difficult to beat her.''

ASSOCIATED PRESS