“Talking isn’t teaching.” It’s a well-known maxim among educators for a reason: it’s absolutely true. And you’ve witnessed this first-hand if you’ve ever had a professor who was highly respected in her field yet nevertheless couldn’t communicate the material in which she was an expert. Or a teacher published time and again, whose name was well known among his colleagues, yet could hardly establish any semblance of a discourse with his own students. It certainly happens in the classroom. And it can happen on the football field, too.
An assistant coach can have all the experience in the world. Rings as a former player, accolades as a coach, be they high school, collegiate, or professional.