Coming into the season, we heard a lot of talk about how the defense was going to show multiple fronts capable of confusing quarterbacks. The results have been... uninspiring. But against Illinois, with Greg Robinson's back against a wall, he finally started to show some of the things that the defense promised before the season began. Part of this is because Michigan was daring Nathan Scheelhaase to throw the ball, about more which later, but Michigan's defense looked like a completely different unit against Illinois than they have all year. On one third-and-short early in the game, Michigan disguised their defensive coverage in an attempt to bait Scheelhaase into a bad throw while staying fundamentally sound and forcing an Illinois punt.
One of the reasons Michigan succeeded here was that they brought pressure off the edge with Gordon. Michigan showed a 3-4 front for a lot of this game and it was really effective. They frequently brought blitzes off the edge and were able to force quick throws or scrambles from Scheelhaase. Part of this is because Michigan was confident that Scheelhaase couldn't beat them through the air consistently. Though I think this is probably Michigan's most effective defensive approach (bring a lot of pressure, mix up looks, and try to get to quarterbacks), against better quarterbacks, Michigan probably won't be so cavalier.
In the end, this play wasn't really any different than the same zone coverage they've been showing all year: a four-man front, four underneath defenders, and cover-3. What changed was the pre-snap alignment of Kovacs and Michigan's ability to disguise the coverage. By bringing Kovacs down from a pre-snap safety position, the x-receiver was unable to read the zone and settle into a soft spot. The Gordon blitz confused the Illinois offensive line, and Gordon was able to get into the backfield untouched, forcing a quick throw. Scheelhaase's first read is the x-receiver, but with Kovacs running directly into the passing lane, he's forced to check it down to the flat where Kovacs' momentum will naturally carry him.
This just looks like a more competent defense than we've seen all year, and much of it is because of a change in base personnel/formation. The 3-4 front that Michigan showed was really effective in this game and should be Michigan's base defense going forward. It's plays like this and the general success Michigan showed against non-option runs that makes me think this defense isn't completely hopeless and Greg Robinson hasn't already been handed his pink slip.