I don't think Lou Holtz said it (don't think I have quoted him before) but where I grew up in football I heard this:
"If you open up the barn door and big fast horses don't run out, its gonna be a long season."
I do like Lou. I think both factors are important. I think there is a minimum level of competency from players that is necessary in order for a system to work. I will say, very solid quarterback play may have helped last year. As a defensive coordinator, last year, there were areas to exploit. I would have worked to jam and shut down the running game. Force Purdue to sustain long drives to score. Overplay and out physical the WR (beat the poop out of them off the ball. The occasional long run would just have to be dealt with. coach pursuit angles hard that week.
There were areas that could have exploited the defense too. Influence block DE's into deep backfield with QB stepping up to throw (kinda easy last year at times). Jimmys and Joes are important. Now with a third year of coaching I think
the page may be turning and everyone may get on same playsheet. QB and DE are obvious keys for me this season.