Michael Keaton on Beating Up Dylan O'Brien in American Assassin

Let's do the math. Michael Keaton is 66 years old. Dylan O'Brien is 26. That's 40 extra years Keaton has on his "American Assassin" costar. And yet the script calls for him to kick O'Brien around. How does he do it?

It turns out Keaton had the same question.

"You have to be realistic about it," Keaton tells Made in Hollywood reporter Kylie Erica Mar. " Realistically, look at the age difference, look at the condition this kid's in. I know it's a movie where you have to buy into a lot of things. But you have to believe that my character could actually do what he can do."

https://www.youtube.com/watch?v=kCfnm6AK77E

The key, says Keaton, was realizing that this same issue drives his character, Stan Hurley, a Cold War veteran who takes CIA black ops recruit Mitch Rapp (O'Brien) under his wing, only to have them battling each other.

"I thought, obviously this guy has to stay in the game," explains Keaton. "How many more good years does he have left? He has to stay in the game physically. But he's smarter, because realistically he couldn't physically probably do day to day what I do in the movie. So he's like: How do I apply smarts to the physical aspect of taking a guy like this down?"

This acting challenge, says Keaton, was critical, which is why Keaton does most of his own stunts, while always respecting his limitations.

"If you can do them yourself, it's kind of fun. I get bored sitting around," he says. "But if someone can do them better than I can, let the stuntmen do them. They're better than I am at it. So I don't have a real macho thing about it."