The scene where Sean beats the dealer to death, was cut by seven seconds. The original scene featured the dealer spitting out teeth and bloody pieces from his cheek. The scene was cut, in order to get an R rating and not an NC-17.
After poor test screenings, New Line had 15 Minuten Ruhm (2001) director John Herzfeld come in and shoot some additional scenes - notably the ending, and cemetery finale - to wrap things up. Also, dialogue scenes were cut, and some scenes also shortened to speed up the pace. This caused the film to miss several release dates. Regular Herzfeld composer J. Peter Robinson also worked on some new score to jazz things up. New Line also had to change the name from El Diablo, due to a law suit from the game developer Blizzard. Potential titles included Push The Limits, Diablo (no El in front), Sean Vetter, Vetter and This Man's Dominion. A Man Apart was finally chosen as the studio felt it suited the theme of the film.
Knockaround Guys (2001) (also from New Line Cinema) and A Man Apart were shelved for a year after the success of Vin Diesel's previous movies The Fast and the Furious (2001) and xXx - Triple X (2002). New Line Cinema felt both movies would be more financially successful with a bigger name action star attached.
Shot in late 2000-early 2001 but not released until April of 2003.
Shortly before filming began, writers Christian Gudegast and Paul T. Scheuring were able to sign a seven-figure deal with New Line Cinema for two scripts, one of which would be a sequel to this movie. Following the movie's delayed release and critical and box office failure, plans for a sequel were canceled, and nothing of the deal ever came to fruition at New Line. The other script, Criminal Squad (2018), was eventually produced by STX Films, with Gudegast also directing.