One of the benefits of running Spaz's Cover 2 defense so long was that every player knew what to do, especially by the time he had been in the system a year or two. Smart players then almost become coaches on the field because they could then help put other guys in the right spot. (The real breakdown of Spaz's D occurred as the talent declined and McGovern and Spaz couldn't get on the same page once Spaz became head coach.
When Don Brown took over the D, he implemented his heavy blitz package. The was about as opposite as could be from Spaz and took a few seasons to adjust.