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NEW YORK, NY - AUGUST 26: Tennis player Jack Sock practices for fans at the US Open American Express Fan Experience 2013 at Flushing Meadows Corona Park on August 26, 2013 in New York City. (Photo by Bryan Bedder/Getty Images for American Express)

NEW YORK, NY - AUGUST 26:  Tennis player Jack Sock practices for fans at the US Open American Express Fan Experience 2013 at Flushing Meadows Corona Park on August 26, 2013 in New York City.  (Photo by Bryan Bedder/Getty Images for American Express)