Keller began his screenwriting career by writing Marc Forster's film Machine Gun Preacher, which was released by Relativity Media in 2011.
In 2022, it was announced that Keller wrote the upcoming biopic about famed female Indycar driver Janet Guthrie who became the first woman to qualify for the Indianapolis 500 in 1977.
[7] Hilary Swank will star in the film which is being produced by Keller, Joel David Moore, Rishi Bajaj and Philip Schneider.
[9] The Paladin is based on a novel by Brian Garfield and tells the true story of how the British government orchestrated a monumental shift in World War 2 through a top-secret program which turned a 15 year old boy into one of England’s deadliest assassins.
In June 2015 it was reported that Keller’s 2006 Black List script "A Willing Patriot" [10] was bought by Open Road Films and is expected to go into production in 2020 with Martin Zandvliet (“Land of Mine”) directing and Liam Neeson starring.