To help him play a brain damaged man, Joseph Gordon-Levitt did not get much sleep and worked out hard at the gym before shooting to help him appear disoriented. He also befriended people with brain damage and read "The Man with a Shattered World: The History of a Brain Wound".
To be more convincing as a blind man, Jeff Daniels spent time at the Michigan Commission for the Blind Training Center in Kalamazoo, observing and learning some basic skills used by blind people on a daily basis.
Sam Mendes and then David Fincher were attached to direct. Once Fincher left the project, writer Scott Frank decided to direct himself.
Chris Pratt auditioned for the role of "Chris Pratt" in the film but the role ultimately went to Joseph Gordon-Levitt.