The scene in which Sean beats the dealer to death was shortened by seven seconds. In the original cut the dealer spat out teeth and bloody fragments from his cheek. The footage was trimmed so the film would receive an R rating rather than an NC-17.
After disappointing test screenings, New Line brought in 15 minuuttia (2001) director John Herzfeld to film additional material — notably a new ending and the cemetery finale — to finish the picture. Dialogue-heavy scenes were cut and some sequences trimmed to pick up the pace, which caused the film to miss several scheduled release dates. Herzfeld's regular composer, J. Peter Robinson, also contributed new score material to liven things up. New Line also had to drop the title El Diablo after a lawsuit from the game developer Blizzard. Working titles under consideration included Push The Limits, Diablo (without the 'El'), Sean Vetter, Vetter and This Man's Dominion. The studio ultimately chose A Man Apart, feeling it best suited the film's theme.
Larenz Tate and Timothy Olyphant later reunited to appear in an episode of the television series Justified (2010), albeit with their roles reversed: Olyphant portrays a US federal agent, while Tate appears on the opposite side of the law.
Knockaround Guys (2001) (also from New Line Cinema) and A Man Apart were shelved for a year following the success of Vin Diesel's earlier films The Fast and the Furious (2001) and xXx (2002). New Line Cinema believed both films would fare better commercially with a bigger-name action star attached.
The film's original title was Diablo. New Line Cinema had to alter the title to avoid legal action from the rights holders of the role-playing, hack-and-slash video game Diablo (1996).
During a raid at a nightclub in Tijuana, the Wilhelm scream is audible when an anti‑drug officer is shot.
The song heard over the end credits is 'Touch', performed by Seal.
Filming took place between late 2000 and early 2001, but the film was not released until April 2003.
Shortly before filming commenced, writers Christian Gudegast and Paul T. Scheuring secured a seven-figure deal with New Line Cinema for two screenplays, one intended to serve as a sequel to this film. Following the film's delayed release and its poor reception with critics and at the box office, plans for a sequel were shelved and none of the agreement ever materialised at New Line. The other screenplay, Den of Thieves (2018), was eventually produced by STX Films, with Gudegast directing.
By the film's conclusion it emerges that the imprisoned drug‑lord Guillermo "Memo" Lucero was behind the "Diablo" escapade. Lucero, as a Spanish surname, literally means "Morning Star" or "bearer of light", a description also applied to Lucifer — the original name given to the Devil. Lucifer is associated with the sin of vanity, and, fittingly, Memo tells Sean that his 'arrogance' led to his wife's death after Sean tracked him down in his native Colombia and ultimately brought him down for good.
This marked Karrine Steffans's final acting role.
Larenz Tate subsequently made an appearance in an episode of the television series Justified, which also starred Timothy Olyphant.
