Howard Cosell's Halftime Highlights Week 6, 1971

"The tragedy of Chuck Hughes" as it was mentioned on the telecast was this:

Hughes, a wide receiver for the Detroit Lions, collapsed on the field after running a route. It was originally thought that he was faking a injury to stop the game momentarily, however Dick Butkus of the Bears starting flailing violently to get the attention of medical staff on-hand. As it turns out Hughes had suffered a fatal heart attack, and to my knowledge is the only NFL player to die on the field of play.