Will Smith dished to ET about the personal impact his latest role had on his life at the Concussion premiere on Tuesday night.
"I did everything I could do to not make this movie," Smith told ET.
In the film, Smith plays Dr. Bennet Omalu, the brilliant forensic neuropathologist who was the first to discover chronic traumatic encephalopathy (CTE) in football players. His fight for the truth to be known puts him in a David vs. Goliath story when he faces resistance from one of the most powerful institutions in the world.
Smith is such a big football fan he had reservations about making the film at first.
"I'm from Philly," said Smith, an avid Eagles fan. "I'm a football dad."
Smith's oldest child, Willard "Trey" Smith III, played football in high school. At the time, Smith wasn't aware of Dr. Omalu's findings.
"As a parent, my son played football. I loved it. I watched him," Smith said. "I had no idea of the long term potential negative impact of repetitive head trauma."
The Oscar-nominated actor started to come around in his willingness to make the movie after he began to look at it from a more human perspective.
"For me, at that point it became a story about a man trying to deliver the truth," Smith said. "It's not a story about football."
Concussion opens Christmas Day. Watch the trailer below.