Everybody on Michigan's star-studded defense last year (Leon Hall, Lamarr Woodley, Alan Branch, etc. ...all All-Americans as I recall) said that the best player on their defense was David Harris. Unlike everybody else Harris sort of come out of nowhere his senior year but he extremely productive.
He's a classic throwback run-stopper and although he's not embarrassingly bad at coverage, stopping the run and making tackles is his specialty...it's a Michigan thing.
Once upon a time the man in my avatar was at a coaching convention where a high school coach was trying to teach college coaches a completely new defensive strategy that he was convinced would revolutionize the game. When somebody asked him why his team did so poorly on defense, then, the coach responded by saying that his team wasn't good at tackling. So, the guy in my avatar said (paraphrasing) "screw strategy, the key to playing effective defense is fundamental tackling!"
That has been the University of Michigan defensive philosophy for the last 35 years or so.