Ed O'Neill's practice of Brazilian Ju-Jitsu partially inspired Mamet to write the movie.
David Mamet had been studying jiu-jitsu for about 6 years prior to making the film.
Chiwetel Ejiofor trained for nearly 3 months before shooting, spending up to 12 hours daily (according to David Mamet) studying and practicing jiu-jitsu.
In the stadium fight scene, David Mamet handed out $100 bills to background in the stands if they answered trivia questions correctly in order to get them to look in the right direction and "appear" interested.
Popular MMA trainer Pat Militech served as a consultant on this film.
Dan Inosanto, who played The Professor, is the foremost student and leading protégé of Bruce Lee.