US Open champion Svetlana Kuznetsova continues to struggle for form following defeat to Eleni Daniilidou at the JPMorgan Chase Open in Los Angeles.
The second seed, who lost early in San Diego last week, went down 6-4 6-4 to Greece's Daniilidou.
Kim Clijsters outclassed Croatian Karolina Sprem 6-2 6-1, while Russian third seed Elena Dementieva and fourth seed Nadia Petrova both progressed.
Mary Pierce was earlier forced to withdraw with a thigh strain.
Dementieva beat Samantha Stosur of Australia 6-4 6-3, while Petrova saw off American qualifier Jill Craybas 6-3 6-1.
Ninth seed Daniela Hantuchova needed three sets to beat American Angela Haynes, eventually winning 4-6 6-1 6-2.
Kuznetsova admits she is desperately lacking in confidence ahead of her title defence in New York.
"It's horrible," said Kuznetsova, who has not won a title in more than 10 months.
"I can't find my game. I don't have confidence and everything comes from the head. If I keep playing like this, I might as well go home."
French Open runner-up Pierce was due to face qualifier Tathiana Garbin in the second round on Wednesday.
"I was hitting serves when I felt it," said Pierce, who suffered the injury in practice on Tuesday. "I'm really disappointed because I'm playing well."
Pierce won her first US outdoor hard-court title - the Acura Classic - in San Diego on Sunday.
Her place in the Los Angeles draw will be taken by Saori Obata of Japan.
The tournament is already without Lindsay Davenport (lower back), Serena Williams (ankle), Vera Zvonareva (left ankle sprain) and Elena Likhovtseva (upset stomach).