The script is loosely based on the first story arc from "The Losers" comic, collectively called "Ante Up". The story appeared in issues 1-6 of the DC Vertigo comic, written by Andy Diggle and drawn by artist Jock.
Originally the project was going to be written and directed by Peter Berg. James Vanderbilt took over scripting duties after the first draft. Tim Story was also attached to direct for a while.