NEW YORK, NY - AUGUST 21:  Stefan Kozlov of the United States returns a shot against Borna Coric (not pictured) of Croatia during their Men's Qualifying Singles round two match prior to the start of the 2014 U.S. Open at the USTA Billie Jean King National Tennis Center on August 21, 2014 in the Flushing neighborhood of the Queens in New York City.  (Photo by Chris Trotman/Getty Images for USTA)