Popular MMA trainer Pat Militech served as a consultant on this film.
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.
Chiwetel Ejiofor trained for nearly 3 months before shooting, spending up to 12 hours daily (according to David Mamet) studying and practicing jiu-jitsu.
'Ed ONeill's practice of Brazilian Ju-Jitsu partially inspired Mamet to write the movie.
In an interview on National Public Radio's "Fresh Air," Chiwetel Ejiofor said that he thought he'd challenge David Mamet to a friendly sparring match (keeping in mind Mamet had been a practitioner of jiu-jitsu for some years compared to Ejiofor's training for a few months). They squared off, and Mamet stepped on Ejiofor's foot with all his weight. Ejiofor couldn't free his foot and was vulnerable to attack. Mamet said words to the effect that "This match is over."
David Mamet had been studying jiu-jitsu for about 6 years prior to making the film.
Dan Inosanto, who played The Professor, is the foremost student and leading protégé of Bruce Lee.