Will Smith stars in "Concussion," based on the true story of Dr. Bennet Omalu, a neuropathologist who first discovered chronic traumatic encephalopathy (CTE).
CTE is a form of brain damage found in athletes and others with a history of repetitive brain injuries.
The first trailer for "Concussion" was released Monday, and it shows Smith's portrayal of Dr. Omalu's battles with the NFL.
One clip from the trailers the line, "You're going to war with a corporation that owns a day of the week."
"Concussion" also starts Alec Baldwin and Adewale Akinnuoye-Agbaje as Dave Duerson. It opens on Dec. 25.