When Michigan played Alabama, the Crimson Tide cornerbacks spent a lot of the game ignoring Michigan's receivers or blitzing off the corner with abandon, so much so that both MGoBlog and myself wrote different posts about the aggressiveness. Alabama is known for blitzing its boundary corners. Notre Dame, to my knowledge, isn't, but did so at least once against Michigan with similar effects.
It's first and 10 late in the first quarter and Michigan is in a four-wide, one-back set. Notre Dame comes out in a 4-3 nickel package.
As the ball is snapped, the boundary corner (bottom of the screen; covering Devin Gardner, more about this later) immediately blitzes.
Denard is reading the strongside defensive end (highlighted) and hasn't seen the corner coming on a blitz.
The defensive end stays high, forcing Denard to hand the ball off, right into the blitz. Elliott Mealer is also getting put on skates and rolled into the backfield.
Fitz Toussaint is wrapped up in the backfield by the blitzing corner. Mealer's inability to hold up here probably stops Toussaint from making any moves on the corner in the backfield, but I don't think it would have changed the end result much.
A lot of what went wrong here is just Al Borges getting beaten on a playcall, but it's distressing that corner blitzes appear to be a surefire way to shut down Michigan's running attack. The other thing that bothers me: Devin Gardner. Watch the rest of the wide receivers. Each one of them heads downfield to block a Notre Dame defender. Just like in the Alabama game, Gardner runs right by his blitzing defensive counterpart. Even worse, the player he eventually identifies to block is 10 yards downfield, not the linebacker that would be waiting for Toussaint if he were able to dodge the blitzing corner. With other wide receivers, you might assume that this blocking assignment might be incredibly difficult or unrealistic, but with someone who is a) new to the position and b) admitted that he doesn't like blocking, this is more evidence of an emerging, disturbing theme. (Also note that teams appear to only be blitzing the cornerbacks that are covering Gardner. I assume this is not coincidence.)
Defenses are not worried about blitzing corners because Michigan never calls audibles/checks at the line, so showing the blitz before the snap is not a concern. More importantly, no one is worried about Gardner as a receiver or Denard as a passer. Corner blitzes against most teams result in good matchups for the offense and easy completions. Against Michigan, you can gamble by putting your safety on a wide receiver because Michigan's wide outs can't get separation.
More importantly, if Gardner is not actually supposed to block the corner here, this offensive scheme is broken, or Borges is incredibly predictable. For example, on this play, which appears to be a traditional zone-read (RB goes one way, the QB goes the other), a corner blitz from the side opposite the RB looks like this:
More commonly this year, michigan has run the inverted veer zone read (below), which leaves the playside DE unblocked. That play is designed to get the running back outside or the QB running vertically. A corner blitz with the same principles (DE staying home on the QB and a corner blitz from the side opposite the RB) produces the same result.
As long as the defensive end is instructed to play the QB on this zone read, the blitzing corner will always have a free shot at a running back in the backfield.
So corner blitzes are bad for the zone read. This doesn't surprise anyone. But I can't see any way that Gardner is not supposed to at least try and block the blitzer. That's his assignment before the play begins and should be his assignment even if the player decides to blitz. If he can't make the block but attempts to, fine. That's just another blown blocking assignment; we've seen plenty of those this year. But his refusal to even try is what's bothersome here.
The real problem is, Borges doesn't seem to have a fix for this and without game-breaking wide receivers or a consistent QB, this is an effective way for teams to force Denard to throw the ball. You can put a fullback in the backfield on Denard's right, but this is twice now that we've seen Gardner completely ignore what should be his blocking assignment because of a blitz.