For starters the rules of college football give an advantage to duel threat QB's which is why power is run only at a small handful of programs. Even Alabama is a duel threat shop after giving up 42 to OSU. For starters I do not believe it is possible in the college game for a dominant defense to shut down a prolific offense run by a duel threat QB. If you are up against a Baker Mayfield or Deshawn Watson all you can do is thwart them a few times and hope your duel threat offense gets a big lead.
Don Brown made his name at BC because he did have some success against duel threat QB's despite having 2nd echelon talent. He did this by recruiting particular types of players who were smaller but more explosive. If the offense is in space, the defense is in space. If a smaller attacker blitzes from an unexpected location, a big hat on little hat is not so useful because the big hat can't get over in time.
There is more exhaustive video and information out there but in simplicity Don Brown wants to disrupt the keys the duel threat QB is relying on. The beauty of the duel threat QB is it is easy to implement and effective even if reading simple keys. If you are always blitzing from different directions, a defensive player shows up in a place the QB is not expecting. There is some great screenshots when BC played FSU and ND where the duel threat QB has read his key correctly yet the play is being obliterated because of an unforeseen blitz. These were all running plays.
There is a classic(I can't tell if Kizer or Zaire) is doing the read option and blitzing linebackers burst through one tackling the QB and the other the RB right at the exchange mesh point.
The philosophy is that a great duel threat QB will keep the sticks moving. Bend but don't break does not work because Baker Mayfield will convert every 3rd and 5. The only way to get off the field is to make a big play. At the risk of giving up a 20 yard chunk you hope to put BM in 3rd and 15 or better yet a TO. That is the only way to combat the advantage of adding another attacker that the duel threat brings. So blitz, blitz, and more blitz and if a big play is made, try to minimize.
Don Brown's defense in 2016 though experienced was mostly Brady Hoke recruits. Fortunately Hoke was a good dline recruiter. Most of the hold overs are gone. Last year UM had difficulty implementing everything Brown wanted because when in the 3-4 they had two slower linebackers, and even when they converted to a 4-3 McCray was a liablity in space(see multiple wheel routes by RB's). It also did not help that 1st year players even if talented made big mistakes.
What do I think for 2018. I think Don Brown finally has a fully weaponized defense. He will be able to field a linebacker corp where every individual can handle run, blitz, or pass defense responsibilities.
There will be two other items that I think will occur in 2018. The first is now that Don Brown's recruits are in their 3rd year he can unleash his gaggle of rabid squirrel pass rushers. I had mentioned Josh Uche as a good example of an undersized tweener who after a couple years probably has space responsibilities down. So I would expect more 3-4 sets where Uche comes in. Now you have 4 4.6ish 40 LB types coming after a duel threat QB.
The other thing I expect more this year is change ups into zone for pass defense. UM had the #1 rated pass defense in the country and it began with the two corners allowing only 22 pass completions the entire year. That is great. But a TO is better. With 10 new starters it was impossible to implement everything. My expectation is do more of what UM did to PSU when McSorely threw that INT. It happened because UM pulled a surprise and played zone.
There are two potential roadblocks to full Don Brown weaponization. Mo Hurst is gone. Someone has to be the interior disruptor. If the center cannot hold you have nothing. The 2nd item is the safeties missed too many tackles that turned 15 yard gains into 30 yard gains or TD's. When the offense wins RPS, safeties have to keep the defense in the game by cutting the big play down.
In summary everyone not Wisconsin is running duel threat. So I don't know why some games are picked where UM did not do as well. Everyone is duel threat! Clearly bad teams with bad duel threat QB's can be more easily handled. If talent is equivalent or there is a maestro at QB, all you can do is try to take it to them at the risk of some big plays. As we saw with Alabama in the 2014-2015 period, even a team that can pick the best defensive prospects in the country is vulnerable to a 40 point outburst, something that happened to Alabama 4 times.
