The original script was written in one week and rewritten 7 times in two months before completion. The total production time (including the two boxing matches) was filmed in five days. The total preproduction and production time was less than 5 months.
All actors boxing preformed their own stunts. Some hits were real though none were preformed at full strength.
Drew Desimone came up with the look of the tattoo himself on set while having the prosthetic applied to his face. When looking at other fighters with numerous tattoos online he believed his character should possess one as well. The design received some input from the make-up artists as to make it more easily replicated.
A full round of fighting was filmed for the opening scene, but it was decided in the editing room that just the heavy slow motion hits were all that was necessary.
The character Crixus gets his name from the reaction of the directors peers seeing the footage for the first time. Seeing how absolutely massive and muscular the actor was they broke in to laughter, believing not only was there no way he would lose a fight, but there was no way the actors real name was Drew and thus dubbed him Crixus "Destroyer of Men". The original character and actors names was never used again by the peers and the name Crixus stuck.