Serbia's Novak Djokovic rips his shirt off as he celebrates his fourth round win over Switzerland's Stanislas Wawrinka at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 21, 2013. (AP Photo/Dita Alangkara)

Associated Press
Serbia's Novak Djokovic rips his shirt off as he celebrates his fourth round win over Switzerland's Stanislas Wawrinka at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 21, 2013. (AP Photo/Dita Alangkara)
Serbia's Novak Djokovic rips his shirt off as he celebrates his fourth round win over Switzerland's Stanislas Wawrinka at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 21, 2013. (AP Photo/Dita Alangkara)