Coz will put a defense on the field that's as good as the players that implement it. His strategy against spread teams has always been a bend but don't break defense. 2 or 3 deep coverage. He gets a lot of heat for that, but we usually did well against those teams when we had good players. We defended Purdue much better than many other Big 10 teams did. Gave up yardage, but usually won the game. The way spread passing offenses have evolved and developed, I don't know if that strategy will be effective now. As the DC, he'll implement whatever scheme the HC wants.
To give you an idea what he can do when he has players, the '98 team was something like #1 Scoring D, #1 Rushing D, #1 Total D, #6 Pass D, #6 Pass Eff D. At his best defending I formation offenses. As others have mentioned, he is a good recruiter.