Maria Sharapova's U.S. Open journey was snapped on Friday as the former champion was upset by Flavia Pennetta, the No. 26 seed, 6-3, 3-6, 6-4.

Maria Sharapova of Russia reacts during the match against Flavia Pennetta of Italy at the US Open tennis tournament in New York Sept. 2, 2011. Flavia Pennetta won 2-1. [Shen Hong/Xinhua]

Sharapova, the third seed, went down quickly in the first set but recovered to take the second set. The match may have hinged on the first game of the third set.

Pennetta was serving to start but Sharapova had advantage and looked as if she may be able to start the set by breaking serve. Instead Pennetta pulled out the game. That propelled her to take a 3-0 lead in the third set.

Sharapova blamed her errors for the defeat, including 60 unforced errors compared to 35 from her opponent.

"I made too many unforced errors. I fought back to get myself back in the match in the third set. I think the first three, four games on every game I had a chance to win that game, whether it was a breakpoint or it was a game point on my serve," said Sharapova.

"I think she (Pennetta) played really smart. That's her game, and she makes you hit a lot of balls. Even when I had balls in the middle of the court, I just didn't do much with them. I thought I could have done a lot more."

Sharapova joins a slew of highly seeded players who have been eliminated from the women's draw. Fifth-seeded Petra Kvitova, the Wimbledon champ, and Li Na, the sixth-seeded French Open champ, were both first round losers.

Venus Williams withdrew before her second round match. No. 8 seed Marion Bartoli was upset by Christina McHale on Wednesday.

For Pennetta's strategy, it's keeping Sharapova running. "I just starting to play not too much shots in the same position to try to move her a lot and try to let her run a lot, and I think it was working really good," said the Italian.

"I started to be really aggressive when she was serving. I try to just let her think too much and maybe make some double fault. That's what happened."

Sharapova made 12 double faults including in the tenth game of third set, which enabled an deciding break for Pennetta.

Pennetta will next face 13-seeded Peng Shui from China, who defeated Julia Goerges of Germany 6-4, 7-6(1), in the fourth round.

Talking about the next opponent, Pennetta said: "It's gonna be really tough. She's in good shape. She play really good in the last summer. It's gonna be tough against her. She really aggressive in her game. She serves really good. I have to be really aggressive and try to move her a lot."

Peng has been through a successful season as she reached last 16 in the Australian Open and Wimbledon Open.

After winning here in 2006, Sharapova has yet to advance past the fourth round at the U.S. Open.