LONDON, ENGLAND - AUGUST 02: Roger Federer of Switzerland returns a shot to John Isner of the United States during the Quarterfinal of Men's Singles Tennis on Day 6 of the London 2012 Olympic Games at Wimbledon on August 2, 2012 in London, England. (Photo by Clive Brunskill/Getty Images)
LONDON, ENGLAND - AUGUST 02: Roger Federer of Switzerland returns a shot to John Isner of the United States during the Quarterfinal of Men's Singles Tennis on Day 6 of the London 2012 Olympic Games at Wimbledon on August 2, 2012 in London, England. (Photo by Clive Brunskill/Getty Images)