Will Smith loves football.

Smith did this, he says, not because Im a good parent.

Friday night lights are ecstasy for me.

Concussion, Dec. 25

Credit: Melinda Sue Gordon

So starring inConcussionwasnt an easy decision.

Thats tough material for a football junkie, but Smith concluded that fatherhood trumped fandom.

As a parent, the responsibility to bring this information to light was overwhelming, he says.

I almost couldnt say no.

To transform into the Nigerian-born Omalu, Smith spent months mastering the doctors demonstrative hand gestures and singular voice.

He even tricked the doctors wife for a moment.

It worked, for about eight seconds, says Smith.

To complete the look, Smith pinned back his ears and added a widows peak to his hairline.

I could walk down the street in Pittsburgh and people didnt recognize me, Smith says.

Concussionwill premiere at AFI FEST on Nov. 10 and debuts in theaters on Dec. 25.