The 42-year-old 'Gone Girl' star will play a mild-mannered accountant who moonlights as a lethal assassin in the Warner Bros movie, reported Variety.
Initially, the role was offered to Will Smith when the project was with Sony. Mel Gibson was initially tapped to serve behind the lens, after the project came to Warner Bros but now the studio has chosen Gavin O'Connor to direct it.
Affleck will next play a murder suspect in David Fincher's 'Gone Girl'. He is also filming his role as the Caped Crusader in 'Batman v Superman: Dawn of Justice' which he is expected to follow up with his directorial venture 'Live by Night'.