Readers of the blog will know that I've been enamored with Greg Mattison all year. Aside from the obvious, tangible gains in performance, Mattison brought with him NFL blitzing schemes that I had been clamoring for during Greg Robinson's disastrous experiment with an "aggressive, blitzing" 3-3-5 defense. Early in the season, Mattison showed more than a few zone blitzes that had me really excited for the rest of the season, but as games rolled by, Michigan lacked the kind of defensive flare that got me excited. Finally, with Iowa in a 3rd and 16, Mattison unveiled a seemingly hellacious blitz that earned Michigan a sack and more importantly, got them off the field in a critical situation.
As the ball is snapped, most of the defenders on the line of scrimmage drop into coverage. Morgan drops from the NT spot, and Martin and Kovacs each begin dropping into their respective coverage zones. Meanwhile, Clark, Demens, Roh, and Van Bergen are the four rushers.
As the play continues, it's clear that Michigan's coverage scheme is a basic cover-2 with five zone defenders underneath. But because Iowa needs 16 yards for a first down, Michigan is able to mix up who they send into coverage without the fear of a blown play.
Iowa's receivers are all running shallow crossing routes, which, if this is defended even remotely how it should be, will net a gain of no more than 5 to 8 yards. Here, you can see that Michigan's underneath defenders are all within arms length of an Iowa receiver, forcing Vandenberg to progress through his reads.
Since all of the Iowa receivers are covered, Vandenberg steps into the pocket where Roh is headed.
A few things of note:
This is a difficult playcall to make unless the opponent has 10+ yards to go for a first down. Sending players like Mike Martin into coverage is risky business if your opponent only needs a few yards to convert, but surprising QBs with a zone drop from linemen is a way to force an errant throw or make them check down to a different receiver. Here, with no one open, Vandenberg has to eat a sack.
The pre-snap alignment also goes a long way toward this result. Obviously having Morgan lined up in the nose tackle spot is a wonky alignment, but in my opinion, the most critical alignment prior to the snap is that of Troy Woolfolk. When a quarterback reads a defensive alignment before the snap, one of the key things they look for is the alignment of the safeties. If there's one deep safety, chances are the team is playing cover-1 or cover-3. If there are two deep safeties, they're likely playing cover-2 or quarters. However, on this play, Woolfolk is the only deep safety, but he will roll to one side of the field as JT Floyd drops into coverage as the second deep safety.