My first year at Cal we won the NC. We had the #1 defense in the country and in the offseason, Louisville hired my DC as their HC. In turn my school hired the DC from a 5-7 Kansas team(I had no control over any of it). I'm sure coaches have no effect on player performance at all. but, what i can say is under my current DC my defense have slid back to the middle of the pack. I'm in the last year of my first contract and if my DC is not replaced, I'm gonna explore my options lol!!!