Wimbledon champion Petra Kvitova became the highest seed to exit the Indian Wells WTA tournament after a 2-6 6-2 6-3 loss to American teenager Christina McHale in the third round on Sunday.
The third-seeded Czech breezed through the opening set at the Indian Wells Tennis Garden but errors began creeping into her game and her 19-year-old opponent took control.
McHale, making her third appearance in the elite event, broke Kvitova in the fourth game of the final set and again in the eighth when the Czech finished with successive double faults.
Serving for the match at 5-3, the world number 35 raced into a 40-0 lead and then sealed victory at the first opportunity, ending a lengthy rally with a delicate sliced backhand into the front court.
"I can't even describe how amazing this feels," an elated McHale said in a courtside interview. "It's amazing She started off really strong but I slowly started finding my rhythm and she began making errors.
"I just kind of kept hanging in there, and then I got more comfortable as the match went on. In that third set I was just trying to hold (serve). I am really excited right now."
McHale said she had gained extra inspiration from the crowd watching her match on the second stadium court at Indian Wells.
"Anywhere in the States the crowd is always great, and especially here, the crowd gets so into it," she said. "It's amazing. I think the fans had seen me from last year. They were great."
McHale, who ousted 11th-seed Russian Svetlana Kuznetsova of Russia at Indian Wells last year for her first victory over a top-20 opponent, will next face 18th-seeded German Angelique Kerber.
Left-hander Kvitova, who outplayed favorite Maria Sharapova to win last year's Wimbledon title for the first time, said she was still struggling for energy after picking up a virus in Doha two weeks ago.
"In the beginning I was fine, I played really good," the 22-year-old said. "After the first set, no. I was sick (in Doha) and I had antibiotics, so I lost a little bit of my fitness. It was tough moving and having winners."
Kvitova, who recorded just two aces while piling up seven double faults against McHale, applauded the American teenager's performance. "She played very solid and she didn't have many mistakes," the Czech said.
"She was moving very well, and she played a lot of shots to back. My serve was not too good, too, so it was tough.
"Next time when I play against her I will have to play the game I played in the first set... have a better serve, not do many double faults, and play aggressive, keep going for the net."