China's Peng Shuai and former world No. 1 Ana Ivanovic both won in straight sets on Wednesday in the second round at the Mercury Insurance Open, while Germany's Julia Goerges made an unexpected early exit.
Peng won 6-1, 6-3 against Australia's Anastasia Rodionova to set up a clash with Italy's Sara Errani. Serbia's Ivanovic beat Japan's Ayumi Morita 6-1, 7-6 (5), avenging a first-round, straight sets loss last week and setting up a match against another Italian, Alberta Brianti.
The shock of the day was provided by American teenager Sloane Stephens, who had an upset 6-3, 7-5 win over seventh-seeded Goerges despite a potentially costly and embarrassing mistake.
Stephens beat her German opponent with a steady ground game and won despite squandering a set point when she allowed a ball that was going out to hit her in the back.
"Today wasn't her best day. I'm happy I got her on this day," the 18-year-old Stephens said. "But everyone has their days and today wasn't hers. I guess it was mine."
No. 11 seed Maria Kirilenko of Russia withdrew from the tournament Wednesday with a left hip injury before her second-round match against Romania's Tamira Paszek. Stephens will face Paszek in the next round.
Sabine Lisicki, the No. 12 seed from Germany, overwhelmed 40-year-old Kimiko Date-Krumm of Japan 6-1, 6-2. Lisicki's next opponent will be local favorite, 19-year-old Coco Vandeweghe, who was a 6-7 (5), 6-4, 6-3 winner over lucky loser Olga Savchuk of the Ukraine.
"I always have really tough matches against Kimiko," Lisicki said. "I think I controlled the point from the start with the serve and the return. I took her weapon away a little bit."
Ivanovic, after winning the first set easily, lost the first five games of the second set before reeling off five consecutive games herself and forcing the tiebreaker. Her next opponent Brianti also had a topsy-turvy match, failing to win a game in the first set before edging Sweden's Sofia Arvidsson 0-6, 7-6 (5), 7-6 (7).
Eighth-seeded Daniela Hantuchova of Slovakia won her first match 6-1, 6-3 over Barbara Zahlavova Strycova of the Czech Republic to set up a meeting with Zheng Jie of China, who upset No. 9 seed Roberta Vinci of Italy, 6-4, 6-2.
No. 16-seeded Polona Hercog of Slovenia lost 4-6, 6-1, 6-4 to Russia's Vera Dushevina, whose next challenge will be top-seeded Vera Zvonareva.
Stephens' previous biggest win was over then-No. 67 Lucie Hradecka of the Czech Republic last season at Indian Wells.
Wednesday's result allowed her to laugh at the set point she gave away when Goerges hit a ball long, but Stephens inexplicably allowed the ball to hit her in the back.
"That was so embarrassing. I don't know what happened," Stephens said. "I was watching it, I tried to get out of the way. ... That's never really ever happened to me before. It was embarrassing, it was funny, it was childish, something an 18-year-old would do."
Goerges, who has two wins this season over top-ranked Caroline Wozniacki, is struggling on the hardcourts after losing last week in the first round of the Bank of the West Classic at Stanford.
"If you saw me play last week, it's not so frustrating," Goerges said. "It's been a big improvement. I am trying to play my game and I am going for it the whole match. It is not working out right now, but it's the right way to come back."