The actor portrays Dr. Bennet Omalu, the medic who forced National Football League officials to take his theories about the dangers of concussion seriously - and change the rules to help current players lead healthier lives when their sports careers are over.

"It's the idea of a silent epidemic and what's so strange is it happens in front of our eyes," Smith tells WENN. "You can actually watch a football game and not see what's actually happening (to the players).

"After this film I don't think people will be able to watch it (the game) the same way. My hope is once the players see it and understand what's happening, they'll be able to make some adjustments and protect themselves in a different way. But you'll never be able to watch football the same way.

"The NFL haven't said anything yet but I hope they'll be happy about the movie and everyone knowing."

And Smith reveals some top players have reached out to him in a bid to catch early screeners of the film, which is released in America this week (ends11Dec15) and around the rest of the world from Christmas Day (25Dec15).

"We've had players that wanted to see the movie; to have a deeper comprehension of the science of what's happening," he adds.

The Wild Wild West star is also gearing up to relaunch his rap career in 2016 with former sidekick DJ Jazzy Jeff and he admits he's very excited to get back onstage.

"There's nothing that compares to being on stage with a hit record," he says. "Those first couple of seconds when people recognise the song as the one they've been waiting for, and that deep 'Ahhhhh!' of realising it; there is nothing in entertainment that matches that feeling. I'm really looking forward to getting out there this summer and performing."