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NEW YORK - SEPTEMBER 14: Juan Martin Del Potro of Argentina returns celebrates with the crowd after winning a point against Roger Federer of Switzerland in the Men's Singles final on day fifteen of the 2009 U.S. Open at the USTA Billie Jean King National Tennis Center on September 14, 2009 in the Flushing neighborhood of the Queens borough of New York City. Del Potro defeated Federer 3-6, 7-6 (7), 4-6, 7-6 (7), 6-2.(Photo by Rob Tringali/Sportschrome/Getty Images)

NEW YORK - SEPTEMBER 14: Juan Martin Del Potro of Argentina returns celebrates with the crowd after winning a point against Roger Federer of Switzerland in the Men's Singles final on day fifteen of the 2009 U.S. Open at the USTA Billie Jean King National Tennis Center on September 14, 2009 in the Flushing neighborhood of the Queens borough of New York City. Del Potro defeated Federer 3-6, 7-6 (7), 4-6, 7-6 (7), 6-2.(Photo by Rob Tringali/Sportschrome/Getty Images)