Svetlana Kuznetsova earned her first title since 2004 when she upset an unsettled Maria Sharapova 6-4, 6-3 to win the Nasdaq-100 Open on Saturday.
Kuznetsova won the battle of Russians to secure her first WTA trophy since triumphing in Bali in September 2004, shortly after breaking through to claim the U.S. Open crown.
She now owns six career titles.
Sharapova, seeded fourth, was a bundle of nerves and seemed distracted by a noisy small plane dragging an advertising banner that droned throughout the opening set until chased off by a police helicopter.
"It was tough today, she was hitting winners off both sides and I couldn't put two points together," Sharapova told reporters. "I was a little tired from my previous matches.
"But it was still a great week, that's the way it goes in sport. I do need some time off."
Kuznetsova will return to 10th in the rankings on Monday, sending Venus Williams down to 11th.
"I was not expecting this," she told reporters. "But I was enjoying it so much. "I've been working very hard. I deserve this title, I gave my best."
Sharapova made 16 forehand errors in the 49-minute first set while Kuznetsova, given a pain-killer for a headache early in the second set, kept her concentration much better.
The 12th seed improved her record against Sharapova to 3-2 as she ran away with the second set against her error-prone compatriot.
Sharapova had been bidding to become only the third woman after Steffi Graf and Kim Clijsters to win the back-to-back American events at Indian Wells and Miami in the same year.