At the height of his career, Leigh Steinberg was the go-to sports agent for NFL superstars, once representing 21 of the 28 starting quarterbacks in the league during the 1990s.

As a super agent, Steinberg — who was the inspiration for the movie character Jerry Maguire — saw it all, especially when it came to injuries.

“I watched athletes I represented play with collapsed lungs,” he told FRONTLINE. “I watched them completely fight with doctors at every time to get into the game. I watched players deceive coaches on the sidelines when they were injured and run back into a game.”

But of all the injuries that Steinberg witnessed, there was one that especially frightened him: Troy Aikman’s concussion in the 1994 NFC championship.

The concussion knocked Aikman from the game — a game the Cowboys would ultimately win. As the city of Dallas celebrated, its star quarterback was laying in a hospital room with his agent. As Steinberg remembered:

He looked at me and he said, “Leigh, where am I?” And I said, “Well, you’re in the hospital.” And he said, ‘Well, why am I here?’ And I said, “because you suffered a concussion today.” And he said, “Well, who did we play?” And I said, “The 49ers.” And he said, “Did we win?” “Yes, you won.” “Did I play well?” “Yes, you played well.” “And so what’s that mean?” “It means you’re going to the Super Bowl.”

But, as you’ll see in the following clip from League of Denial: Inside the NFL’s Concussion Crisis, it was what happened next that really terrified Steinberg.

In the film, which premieres Tuesday, Oct. 8 beginning at 9 pm EST, FRONTLINE investigates the hidden story of the NFL’s response to head injuries like the one that hospitalized Troy Aikman. Through interviews with former players, scientists and other experts on the concussion issue, the film examines what the NFL knew about the risks of such injuries, and when it knew it.

You can find out when League of Denial airs on your local PBS station here.