Spain's Roberto Bautista Agut knocked out Tomas Berdych in the second round of the BNP Paribas Open, beating the fourth-seeded Czech player 4-6, 6-2, 6-4.
Berdych had won 11 matches in a row in February and is 16-4 this year.
Sixth-seeded Juan Martin del Potro withdrew because of ligament damage in his left wrist. The Argentine player also pulled out of the Dubai tournament last week.
John Isner, the No. 12 seed and the only remaining American from the original 14-man contingent, advanced with a 7-6 (5), 6-3 victory over Russia's Nikolay Davydenko.
In women's play, 19-year-old Eugenie Bouchard of Canada beat ninth-seeded Sara Errani of Italy 6-3, 6-3, and 2011 champion Caroline Wozniacki topped qualifier Yaroslava Shvedova of Kazakhstan 7-6 (7), 3-6, 6-1.