Unseeded American Lauren Davis secured the first big upset of the BNP Paribas Open when she ousted third-seed Victoria Azarenka of Belarus in the second round at Indian Wells.
Davis broke serve seven times en route a 6-0, 7-6 victory as she pounced on the 2012 champion's second serve.
Azarenka, who was hampered by a foot injury, did not help her cause with 12 double faults. It is the first time 20-year-old Davis, ranked 66th in the world, has beaten an opponent inside the top 20.
Earlier in California, second-seed Agnieszka Radwanska earned a belated birthday present when she broke the serve of British qualifier Heather Watson seven times to win their second round match.
Radwanska was not exactly dominant, dropping serve five times herself, but she had enough of an edge to beat Watson 6-4 6-3.
In another match, Caroline Wozniacki, the 10th seed, beat Bojana Jovanovski 6-1 6-3.
In the men's doubles, Swiss grand slam winners Roger Federer and Stanislas Wawrinka teamed up for the first time in 18 months and entertained a large crowd in beating Rohan Bopanna and Aisam-Ul-Haq Qureshi 6-2, 6-7, 10-6.