CARLSBAD (California): Japan's Ai Sugiyama stunned second seed Svetlana Kuznetsova 2-6, 6-4, 6-3 in one of several upsets in the third round of the Acura Classic on Thursday.
Russian 18-year-old Anna Chakvetadze upended ninth seed Elena Likhovtseva 6-3, 6-1 and China's Peng Shuai beat number 16 seed Dinara Safina 7-6, 6-0.
But fifth seed Patty Schnyder, sixth seed Mary Pierce and number seven Kim Clijsters all survived.
Schnyder beat Francesca Schiavone 6-7, 6-1, 6-4 and will meet France's Pierce, who beat Nathalie Dechy 7-5, 6-3.
Clijsters continued her fine run of form on the US hardcourts, she is unbeaten since the 2003 US Open final, when she powered past Jelena Jankovic 6-1, 6-3.
Japan's Akiko Morigami, meanwhile, ended Indian qualifier Sania Mirza's run with a 6-2, 4-6, 6-4 victory.
Using a straight ahead attack, Pierce beat Dechy for the fourth time in five meetings.
The 30-year-old Sugiyama counterpunched brilliantly against US Open champion Kuznetsova, who was rusty after a month's break since Wimbledon.
I had too many ups and downs. That month was the longest break I've ever had from tennis and I need some more matches before I get my form back, said Kuznetsova Reuters