Reigning Wimbledon champion and WTA Player of the Year Petra Kvitova exited Indian Wells when Christina McHale rallied to upset the Czech in three sets 2-6, 6-2, 6-3 on Sunday.
It looked like the third seeded Kvitova might be headed for a routine victory in their first career meeting when she broke McHale twice in winning the first set in 34 minutes.
But McHale broke Kvitova twice in each of the final two sets, finishing the almost two hour match with six aces and a 66 percent winning percentage on her first-serve points.
In the eighth game of the final set, Kvitova double faulted on the final two points, handing the game to McHale and making it 5-3.
Serving for the match, McHale won all four points in the final game and took victory with a backhand slice winner that Kvitova was unable to reach.
Kvitova finished with just two aces and seven double faults.
World number three Kvitova claimed a WTA-leading six titles last year but has yet to win one in 2012.
The 22-year-old from Fulnek was forced to withdraw earlier this year from tournaments in Doha (Achilles injury) and Dubai (illness).