In 2013, PBS' Frontline went head-first into the NFL's checkered history of trying to deny the game's connection to debilitating brain injuries.
Two years later, former Wisconsin linebacker Chris Borland is part of a new Frontline feature as football's concussion issue reaches the big screen.
Frontline this week released a feature called "How Afraid Should the NFL be of Chris Borland?" In it, Borland detailed his eye-opening decision to retire from football earlier this year just as his pro career was starting to take off.
He said he gave up playing the game after weighing the potential for brain trauma, and that made him a national symbol for concerns with the risks of football.