China's Peng Shuai upset fourth seed Agnieszka Radwanska in two straight sets at the U.S. Open Wednesday. Play took place at Louis Armstrong Stadium, Flushing Meadows, N.Y..

Radwanska, Rogers Cup champion erlier this month, had a bit of trouble in the first set as she committed an unforced error causing Shuai to break her serve and win the set.

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The other half of the French Open women's doubles champion, Shuai got an opportunity to break the Polish national at 2-2 in the second set and took it to lead 4-2.

Shuai, 28, kept her calm and eventually held serve to win the match 6-3 6-4. She was able to serve up three aces and 28 winners in a match that lasted an hour and 36 minutes.

Radwanska, 25, has not made the quarter-finals of the U.S. Open throughout her career. She was eliminated last year by Russian Ekaterina Makarova in the fourth round

Shuai has not made the quarter-finals in any of the Grand Slams that she participated in. The last time she made the fourth round of the US Open was in 2011 when she was seeded 13th and lost to Italian Flavia Pennetta.

Shuai will now face the other half of the Wimbledon women's doubles champion Roberta Vinci.

The 28^th seed Vinci had a hard match against Irina-Camelia Begu of Romania at Court No. 7.

24-year-old Begu broke Vinci twice in the first set but Vinci took a serve away from the Romanian in the second set to force the match into a tie-breaking set.

In the third set, the 31-year-old Vinci got back in form and finished Begu 2-6 6-4 6-1.

Shuai and Vinci have not faced each other in a singles competition. They last saw each other during the championship of the women's doubles in Roland Garros along with partners Hsieh Su-wei and Sara Errani respectively.

TagsPeng Shuai, Hsieh Su-wei, Sara Errani, tennis, Sports