Duerson’s N.F.L. career ended in 1993, and he became a successful businessman. He was eventually a player representative on the panel that considered retired players’ claims under the N.F.L.’s disability plan and the 88 Plan, a fund that helps retired players with dementia.

“What the movie doesn’t appreciate was how difficult a position he was in,” Tregg Duerson said. “You have someone on a board with a fiduciary responsibility who can’t just give out dollars for the sake of giving out dollars. I think his hands were tied.”

In addition to reading applications from players and voting on whether they would receive financial assistance, Duerson testified at 2007 congressional hearings that focused on whether the disability board was unfairly denying benefits. Duerson suggested that there was no definitive link between playing football and dementia.

“In regards to the issue of Alzheimer’s, my father’s 84, and, as I had mentioned earlier, Senator, spent 30 years at General Motors,” Duerson said to Senator Amy Klobuchar of Minnesota, according to a transcript. “He also has — he also has Alzheimer’s and brain damage, but never played a professional sport. So the challenge, you know, in terms of where the damage comes from, is a fair question.”

But around this time, Duerson’s life began changing. His company was forced into receivership, and his home went into foreclosure. He also pleaded guilty to a misdemeanor domestic battery charge after pushing his wife during an argument. He filed for personal bankruptcy.

It is unclear how much Duerson’s behavior was affected by the degenerative disease that he was found to have. It is not addressed in the movie, something that irks his family.