Nate Jackson played for the Browns for a hot second during Mangini's last year in Cleveland. The former tight end played for years in the league before bowing out. Now he writes — for the New York Times, for Deadspin, for Slate, and others.
Here's a bit about Coach Mangini and some reductio ad absurdum from a recent piece from Deadspin.
I was only in Cleveland for one week, but as I wrote last year, I was there long enough to figure out that his coaching style was so interactive as to be intrusive. He peppered his players with fourthdownulator-esque studies, made them memorize those figures, then called upon them in meetings and forced them to stand and recite them. Players were visibly shaken by the process. This was not the football they knew. They had notes scattered about their laps and desks, nervously hoping they wouldn't be asked to stand and tell Mangini what percentage of the time field goals are made by a left-footed kicker from the right hash-mark facing south with an east-to-west wind in the second quarter of Thursday night games in November. It's hard to play your best with these things on your mind.
Mangini was a bad head coach. He couldn't reconcile his scientific approach to the game with the real-time lack of science that was needed to play it. He took it too far and lost his team.