Clayton was 67.
“John was a pioneer as an NFL insider but also one of the kindest men you could ever work with,” ESPN vice president and executive producer Seth Markman said, according to the network.
“He literally never said no to a show that asked him to come on — from 6 am to midnight, if you asked for the Professor, he was there for you. I’ll also personally remember how he loved and cared for his beloved wife Pat as she has battled multiple sclerosis. We will all miss John greatly.”
Clayton, a native of Pittsburgh, began his sports reporting career in 1972 covering the Pittsburgh Steelers, Seattle Sports reported.
The Pro Football Hall of Fame, of which Clayton was a selection committee member, expressed his condolences on Instagram, saying Clayton’s, “impact and contribution to the game of football will be missed.”