Novak Djokovic returns the ball to David Ferrer during the second day of the Mubadala Tennis Championship in Abu Dhabi, United Arab Emirates, on Dec. 28, 2012. (Associated Press)

Photo by: Kamran Jebreili

Novak Djokovic returns the ball to David Ferrer during the second day of the Mubadala Tennis Championship in Abu Dhabi, United Arab Emirates, on Dec. 28, 2012. (Associated Press)