Foster, who also starred in 3:10 To Yuma oppsite Russell Crowe and Christian Bale, plays the apprentice to a seasoned hitman in the film. He spoke to WENN about the injury, which was incurred while filming his own stunt.
"The night before the stunt we were doing the intro to the fight, where this character throws me against the wall and I fall," said Foster. "I asked to actually do the stunt and they said, 'You don't need to', and I said, 'I do'."
Foster continued: "Anyway, I fell awkwardly on my shoulder and it snapped. I didn’t say anything and asked if we could end and they said they needed one more take, so I do it again and snap… masochism! We got in for the night and I go to bed and think I’m gonna shrug it off. I wake up and I can’t move my shoulder."
Foster then added that the producers of the film hired a doctor to help him with the injury.
"He got out a big syringe and pushed it in and squeezed it down; another shot, another shot and it loosened up. Whatever was in that syringe felt really good!" he said.
The Mechanic opens in cinemas on January 28.