FILE - In this June 15, 2014, file photo, Grigor Dimitrov, of Bulgaria, poses with the trophy after his win against Feliciano Lopez, of Spain, at the end of their Queen's Club grass court ... more 
FILE - In this June 15, 2014, file photo, Grigor Dimitrov, of Bulgaria, poses with the trophy after his win against Feliciano Lopez, of Spain, at the end of their Queen's Club grass court championships singles final tennis match in London Heading into the U.S. Open, Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray have won 36 of the past 38 Grand Slam titles, a stretch dating to the 2005 French Open. Nowadays, there seems to be a growing sense _ or hope, maybe _ among the best of the rest on the men's tennis tour that the quartet might be more vulnerable than ever. (AP Photo/Sang Tan, File) less 
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Associated Press | Photo By Sang Tan, File
Fri, Aug 22, 2014 1:30 PM EDT