**SAMANTHA STOSUR**      **Age:** 26. **Country:** Australia. **U.S. Open seed:** 5. **Highest W.T.A. ranking:** 5.       The key to the 2010 French Open runner-up's success at this year's U.S. Open? Winning the first set. When she does, her opponent is pretty much screwed: so far this year, Stosur has a 28-to-1 record this season of winning the match when she's up a set. And watch out for her serve. With 229 aces in her back pocket this year, she's one of two players in the main draw to have hit 200 or more service winners.
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