Roger Federer of  Switzerland walks off the Rod Laver Arena after his semifinal loss to Rafael Nadal of Spain during their semifinal at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2014.(AP Photo/Andrew Brownbill)

Roger Federer of Switzerland walks off the Rod Laver Arena after his semifinal loss to Rafael Nadal of Spain during their semifinal at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2014.(AP Photo/Andrew Brownbill)