Roger Federer of Switzerland reacts to winning a point as he plays David Ferrer of Spain during their ATP World Tennis Finals singles match in London, Thursday, Nov.  8, 2012. (AP Photo/Kirsty Wigglesworth)

Photo by: Kirsty Wigglesworth

Roger Federer of Switzerland reacts to winning a point as he plays David Ferrer of Spain during their ATP World Tennis Finals singles match in London, Thursday, Nov. 8, 2012. (AP Photo/Kirsty Wigglesworth)