Juan Martin Del Potro of Argentina plays a return to Roger Federer of Switzerland, during their singles tennis match at the ATP World Tour Finals, in London, Saturday, Nov. 10, 2012. (AP Photo/Sang Tan)

Associated Press
Juan Martin Del Potro of Argentina plays a return to Roger Federer of Switzerland, during their singles tennis match at the ATP World Tour Finals,  in London, Saturday, Nov. 10, 2012.  (AP Photo/Sang Tan)
Juan Martin Del Potro of Argentina plays a return to Roger Federer of Switzerland, during their singles tennis match at the ATP World Tour Finals, in London, Saturday, Nov. 10, 2012. (AP Photo/Sang Tan)
View Comments (0)