NEW YORK (WFAN/AP) - Tennis fans at the US Open witnessed a pretty big upset Friday.

WFAN Extra: US Open Guide

Maria Sharapova, the 2006 US Open champion, was upset in the third round by Flavia Pennetta.

Sharapova lost 6-3, 3-6, 6-4 to the 26th-seeded Italian on Friday. Sharapova had been 12-0 in three-set matches this year, including her first-round win.

Pennetta broke serve to clinch the victory in a match full of breaks, with the third-seeded Russian struggling with her serve.

Sharapova had reached her first Grand Slam final since 2008 shoulder surgery when she was the runner-up at Wimbledon.

Pennetta will next face 13th-seeded Peng Shuai of China, who beat 19th-seeded Julia Goerges 6-4, 7-6 (1).