1 - You have to truly understand what it is you're teaching. Math teachers have to understand math, historians need to correctly understand history and football coaches need to understand the game of football. 2 - You have to love those you are teaching. If you have the second, you'll find a way to communicate, clearly, all the knowledge of the subject that's in your head to your students' ears. That is absolutely guaranteed.

I taught in a high-performance environment for 16 yrs and those are the only 2 skills a great teacher, or coach, needs. I saw guys that had tons of skill but didn't care about those they taught; they were almost worthless. On the other end of the spectrum I saw guys who cared about their students but didn't yet have all the skill they needed. Those weren't the best teachers, either.

My point is that in needing knowledge and love of those you teach, Ty Detmer had plenty of both.