India's Sania Mirza stunned former world number one and five-times Grand Slam winner Martina Hingis 6-2, 2-6, 6-4 to reach the third round of the Los Angeles Classic on Tuesday.
Sania continued her fine summer hardcourt season and fought off two break points at 1-1 in the third set with two blazing forehand winners.
She needed four match points to close out the match, but won it when Hingis missed a forehand.
"She was all hungry out there and so am I, but she just seems fresher," Hingis told reporters.
"She hits incredible angles with her forehand."
After four straight weeks of play, Sania said she was tired but had learned how to push through the matches.
"To beat one of the quickest players on the tour and to have to dig deep to do it, that feels great," she said.
"It tells me that I can do it again."
Sania will face the winner of the match between Israel's Shahar Peer and Virginie Razzano of France in the third round.
Hingis, who has been suffering from a back injury, said she may have returned too fast and was considering pulling out of Toronto next week to recover and get more practice in for the US Open.
Wimbledon finalist and number six Marion Bartoli and Russian Dinara Safina also made early exits, although three seeds did survive.
Defending champion and number nine seed Elena Dementieva took a 6-3, 6-1 victory over Ekaterina Makarova of Russia in the first round.
Tenth-seed Shahar Peer of Israel also won her first round contest when she defeated Dominika Cibulkova of the Slovakia 6-2, 6-3 and 15th seed Katerina Serbotnik of Slovenia beat American Bethanie Mattek 6-4, 7-5.
Bartoli lost 7-6, 6-3 to Russian Maria Kirilenko and Safina went out to Ukrainian Kateryna Bondarenko 6-2, 7-5.
After suffering her third early exit in as many weeks, Bartoli said she was having problems with her confidence.
"When you win a lot of matches and you are used to playing the big points, then you are confident," Bartoli said.
"When you don't play the big points, you think a little too much."
After rediscovering her form in recent weeks, Russian Kirilenko said she has no problems with her confidence.
"I did a good job in the end," she said. "I attacked and played the big points with confidence. This week I feel perfect."
Top seed Maria Sharapova will make her debut on Wednesday against Greece's Eleni Daniilidou, a 3-6, 6-2, 6-1 winner over France's Arevane Rezai.
Second seed Jelena Jankovic of Serbia will face China's Shuai Peng, who defeated Yaroslava Shvedova of Russia 6-3, 6-4.
Third seed Ana Ivanovic of Serbia will play her first match since Wimbledon, against American Ashley Harkleroad.
