Serbia's Novak Djokovic, right, embraces Switzerland's Stanislas Wawrinka after winning their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 21, 2013.(AP Photo/Andy Wong)

Photo by: Andy Wong

Serbia's Novak Djokovic, right, embraces Switzerland's Stanislas Wawrinka after winning their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 21, 2013.(AP Photo/Andy Wong)