In Will Smith‘s latest film, Concussion, the Philadelphia rapper and actor portrays Nigerian doctor Bennet Omalu who confronts the National Football League about the dangers of head trauma its players faced.

In a Variety Actors on Actors interview with Sicario‘s Benicio Del Toro, Smith details his hesitancy to accept the role after getting a call from producer Ridley Scott.

“I got the call from Ridley and he said, ‘I’ve got a gift for you,'” Smith says. “And he sent me Concussion. I read it immediately, and I remember thinking, ‘This ain’t no damn gift!’ I’m a football dad. So for me, it was a beautiful screenplay, but it opened up a huge conflict for me.”

Besides being a Philadelphia Eagles fan, Smith’s oldest son, Trey, played football in high school at Oaks Christian School.

“During that time I had never heard about the concussion issue at all,” he says. “It was part of what really inspired me and made me want to do the film, forced me to have to do the film was because as a parent, I had no idea. I had no idea that there was an issue with repetitive trauma in football. It was quite a revelation.”

Concussion is due out in theaters December 25.