Northwestern is in a three-wide set with a tight end on the opposite side of the field and Venric Mark in the backfield. Michigan is in its nickel package. But before the ball is even snapped, you can see a huge problem: Michigan is badly outnumbered to the boundary side of the field. From the offensive center toward the boundary, Michigan has only four defenders. Nebraska has four men on the line of scrimmage, Colter, and Mark. There's absolutely no way Michigan can defend this play toward the sideline.
As the ball is snapped, Northwestern's center and right guard double Black, while the right tackle and tight end release to the second level to block Kovacs and Desmond Morgan. Brennan Beyer is left unblocked and is the player Colter is reading.
Beyer stays to the inside and forces a pitch outside to Mark. This is bad. The right guard is cut blocking Morgan and the tight end is headed straight for Kovacs.
Beyer is now in pursuit of Mark but has no chance. Morgan is Superman-ing over the right tackle. Kovacs is engaged with the tight end. The only player with any chance of making this tackle is JT Floyd and he's seven yards from the line of scrimmage and has to make up ground horizontally to get to where Mark is.
Kovacs keeps Mark to the inside of the field, but it doesn't really matter. There isn't anyone there to tackle him. Mark is now two yards past the line of scrimmage with a head of steam and Floyd is still five yards away. best case scenario, this is a six-yard gain.
But it's not because Floyd overruns the play.
Mark will scamper ahead for 30 yards.
The obvious problem here is the way that Michigan is aligned, but that's a function of playing a spread team. They're in man coverage against the receivers with a safety over the top who also defends against a bubble screen (4 players) and have four down linemen (8 players), leaving only three players to defend against this option look. This is one of the inherent dangers of playing option teams like this, but because Michigan is so outnumbered, it becomes even more important for Beyer (or whoever is left unblocked). Forcing Colter to keep pushes him back toward the strength of the defense and toward a spot on the field where Floyd can more easily come downhill and make a tackle. If Colter slows down at all, he'll be tackled by the pursuit defenders (who eventually tackle Mark 30 yards downfield). Michigan defended the pitch this way for a large part of the first three quarters before making the shift in the fourth. Option teams present these problems and its up to Mattison to have a better gameplan to defend basic parts of the opposing offense.