Some champions insist their toughest opponent is in the mirror.

Maria Sharapova puts that theory to the test in a new commercial for Porsche.

Video: Top 10 Hottest Couples of 2015

Maria meets her match when she squares off against herself on court at about the three-minute mark of the video below.

The Greatest vs. The Greatest commerical creates a series of dream match-ups featuring champions facing themselves in their respective sports.

In addition to Sharapova, former heavyweight champion Muhammad Ali (played by an Ali stand-in) fights against himself and grand master Magnus Carlsen plays chess against himself in the ad for the Porsche 911.

Check out this behind-the-scenes video of the commercial.