Radwanska, ranked No. 32 in the world and seeded 30 here, never buckled under the weight of playing the defending champ and revealed a fearlessness out on court.
"I had nothing to lose," she said, "Just she was the favorite, and I think she was more nervous. I just played my game."
Sharapova seemed to take control by winning eight games in a row, giving her a 2-0 lead in the final set. Then, she fell apart and gave up the match by losing six games in a row.
Sharapova became the first No. 2-seeded woman to lose before the round of 16 at the Open since Andrea Jaeger in 1981. Her father could barely stand to watch, moving from his front-row perch to a seat farther back during the final points.
Sharapova looked to be the far more powerful player throughout the match. But along with her 36 winners, she hit 49 unforced errors and 12 double faults, many of those doubles happening at inopportune times.
This was the earliest Grand Slam loss for Sharapova since losing in the third round of the 2004 U.S. Open.
manufacturer, has announced a new sponsorship deal with Polish tennis star Agnieszka Radwanska.
Agnieszka is joining the family of Longines partners, including legendary couple Andre Agassi and Stefanie Graf.
“It’s a privilege to be a Longines Ambassador of Elegance,” Radwanska said in the Longines announcement.
“To represent this fantastic watch manufacturer alongside such tennis legends as Stefanie Graf and Andre Agassi is a real honour.”
Longines is proud of its long history of sports timekeeping and is the official partner of the French Open at Roland Garros.
Radwanska is set to compete in the French Open for the third time next week and will be making her first international appearance as a Longines Ambassador of Elegance.
Agnieszka Radwanska (born 6 March 1989) is a Polish tennis player.
She defeated Tamira Paszek of Austria to win the 2005 Girls' Singles Championship at Wimbledon. As a professional, her highest WTA ranking to-date is World No. 11, achieved on 23 June 2008.
In 2007, Radwanska became the first Polish player in history to claim a Sony Ericsson WTA Tour singles title when she won the Nordea Nordic Light Open. In 2008, she won three more singles titles: the Pattaya Women's Open, the Istanbul Cup, and the International Women's Open.
At the 2008 Australian Open, Radwanska became the first Polish woman to reach a Grand Slam singles quarterfinal during the open era and only the second Polish woman (the other being Jadwiga Jedrzejowska during the 1930s) ever to reach a Grand Slam singles quarterfinal.
On May 24, 2008, Agnieszka Radwanska became the first Polish female tennis player to surpass US$1 million in career prize money.
Maria Sharapova of Russia plays a return to Agnieszka Radwanska of Poland during their match at the U.S. Open tennis tournament in Flushing Meadows, New York, September 1, 2007.(Xinhua Photo)
It was also her worst showing at a Grand Slam this year. The Russian lost in the final of the Australian Open to Serena Williams, the semifinals of the French Open to Ana Ivanovic, and the fourth round of Wimbledon to Venus Williams.
For Radwanska, she's moving on to celebrate the biggest win of her career.
"Before the match I spoke with my sister and said, 'If I beat [Sharapova], we will buy two Louis Vuitton bags,' because it's so expensive. And she was, 'Okay, if you do it. O.K.' Now, we are going to buy two bags."
Radwanska next faces the winner of the Nicole Vaidisova-Shahar Peer match.