Will Smith’s new movie Concussion delivers a hard blow to American football

Concussion delivers a hard hit to the NFL as it deals with data linking repeated blows to the heads of its players to dementia and a host of other problems.

The league's rocky dealings with Dr Bennet Omalu, who identified a degenerative disease in football players known as CTE, or chronic traumatic encephalopathy, are the focus of the movie's second hour.

Starring Will Smith and Alec Baldwin, Concussion had its premiere Tuesday night at AFI Fest in Hollywood. Among the audience at the TCL Chinese Theatre was the wife of Justin Strzelczyk, a Steelers offensive lineman killed in a car crash, and the wife and daughter of Hall of Fame linebacker Junior Seau, who fatally shot himself. Strzelczyk was later found to have brain damage, while Seau had CTE.

Smith plays Omalu, a Nigerian-born forensic pathologist in Pittsburgh who knows nothing about football when he performs the autopsy on former Steelers centre Mike Webster. Omalu discovers CTE in Webster's brain, setting him on a journey that exposes the concussion crisis.

Omalu quickly finds the NFL demanding he retract his CTE findings while accusing him of fraud. The doctor is the target of threatening phone calls and his wife is followed while driving alone.

The movie names real people and uses footage from real NFL games showing the kind of blows to the head that can injure and permanently damage players.