The one takeaway from the Nebraska game that isn't crushing dominance was Michigan's zone defense on in-breaking routes (slants/digs) needed a lot of cleanup. What went wrong wasn't hard to figure out, but there's some understandable confusion I think about how, or in some cases whether, it was supposed to go right.

ZONE REFRESHER

Cover 3 at its core has three deep zones, two Curl/Flat zones, and then you can vary how many players you want to drop into Hole zones.

Drawing circles is a bad way to represent zones, however, because it makes it seem like defenders are tasked with sitting in the middle of their circles and projecting strength over their fiefdoms. We call that "covering grass." You do that, you end up like Stephen of Blois with rebellions springing up everywhere around you. You have to play zone defense with the constant movement of a Henry Plantagenet: anticipating trouble, heading it off, harrying it out of your kingdom, then snapping quickly to stop the next threat before it gets out of hand.

The route you take to your zone is important too, because you can't give receivers the run of the roads. Note how the paths of the SS and Nickel will have them above the Y and the H respectively, while the CBs would be escorting the outside receivers to deep 1/3 zones. Those defenders are heading elsewhere, but for the duration of a quick seam they're right in the way.

That takes care of the seams and fly routes, but there are a few known vulnerabilities where offenses know you can squeeze a ball between the zones.

[After THE JUMP: Feeling attacked]

Route combinations to attack Cover 3 are usually about threatening multiple weak spots at once, and forcing defenders to leave one of them unguarded. A defense like Michigan that plays a lot of coverage games is going to make it hard to find the weak spots when they appear because the quarterback is never sure if there's a defender coming through there. When you can find the defender and move him off his spot however, you're going to get a wide open throw.

Here's a simple TE out that found space because the curl/flat defender didn't get to his spot despite having a ton of help inside.

#5 the DE on the top

This is a three-man rush with the extra defender taking a hole zone. However it's also a defensive end, Josiah Stewart, given the flat zone. He does a good job to mirror the TE early to prevent a slant inside…

But Stewart only walls off for the initial release, and once Fidone gets behind him Stewart starts covering grass, imagining the threat has passed and the TE is going to turn inside to run a crossing route.

He isn't. Stewart even takes a step inside before realizing he's been covering grass this whole time. Zone rule of thumb: If you are in zone and standing closer to your own teammate than the opponent in your zone, you done messed up.

That one wasn't so complicated, but I wanted everyone on the same page as we dig into what was happening on the slants and one post route that accounted for most of Nebraska's yards on the day. This next one was also on Stewart but this time he got beat inside on a different type of zone.

#5 DE on the bottom

Again, Michigan dropped eight, although Nebraska this time has five guys attacking the coverage instead of three. Also Junior Colson didn't notice until just before the snap that the running back was lined up outside (you can see #25 running off towards the top of the screen). The top does get all discombobulated, but it doesn't actually end up mattering. All the offense wants out of this is to get Colson out of there.

Michigan's matchups get messed up by Nebraska's deployment, going empty 5-wide with 12 personnel.

The defensive plan is supposed to be a sort of split coverage with a pair of defensive ends dropping to wall off in-breaking routes before getting into their zones.

Remember what I said about protecting quick releases though. In order to keep Stewart inside Michigan has Harris playing over the slot receiver's seam route, meaning Harris needs help on anything that breaks immediately inside. Like a slant route.

Then right about here I think Stewart sees the slot receiver put his head outside and assumes the body is going there as well.

It's enough to get Stewart, a defensive lineman, to take a lethal step outside before turning around to face the quarterback and play the ball.

And Haarberg throws as soon as the slot is clear.

I'm not going to give Harris a negative for this one because he was supposed to have help on exactly this route. If Stewart had dropped into the slot's slant path we wouldn't be here.

As for Derrick Moore on the other side, he wasn't innocent in this either. And neither was Sainristil.

There's a little more going on here so I drew it up.

But it's the same issue as the slant against Stewart, except multiplied because this time the receiver and the quarterback got both sides of the bracket to hop outside with a fakey. Michigan was also ratcheting up the confusion, having Moore take a few steps like he's pass-rushing to temp the quarterback into reading man coverage with no help inside.

As soon as Barrett (#23) takes off after the running back's release the QB should think he has the slant open. He should also be wrong.

The problems start when Michigan's defenders start reading the quarterback's eyes and feet. Haarberg is planted like he's ready to throw outside the same way he did on Harrell earlier.

The QB even pumps that direction to really sell it. And it sells. Watch both Sainristil and Derrick Moore on the replay. Sainristil first.

That pump creates all the space. Moore hops all the way out of the lane. Sainristil freezes just enough to create the kind of separation that translates into mondo yards after the catch.

Note in each of these cases, the way Michigan was playing slants reversed the jobs of their flat and hole coverage defenders off the snap. Remember this?

Instead of the curl/flat guy they were having the hole defender stay outside and prevent a quick seam. This was supposed to be to the defense's advantage, freeing the curl/flat defender from having to worry about anything but quick in-breaking routes until the pattern started to develop. But because those guys didn't get to where they were supposed to, the hole defenders were still holding outside leverage, putting them in a terrible position to defend slants.

After these three events I think Michigan decided to put away this package until they can rep it better. I suspect that they didn't see a lot of slants in Nebraska's film before and figured they were going to be bracketing snags and hitches and the like. They were annoying—slants with YAC are especially dangerous because the guy's momentum is already moving downfield—especially after they got hit with the same for a touchdown against Rutgers. But it's not that hard to fix: rep your DEs in coverage more.

The one that was more concerning involved defensive backs. And that had a lot more to do with the regular rules for zone coverage. It's this play that began the second half. Note again that Nebraska went to 12 personnel, and Michigan is in their 5-2, with Paige in the slot and Sabb high:

The hole defender here is Junior Colson, who had run action to deal with and couldn't have helped even if he did start backpedaling the second the back went to chip Harrell (I kinda want him backpedaling then anyways).

Once again, as it's drawn up there should be a bracket on the receiver (Marcus Washington) this went to. Nebraska only has two receivers in routes, with Keon Sabb playing a middle third where no other receiver is coming, and Will Johnson playing a deep third that's threatened underneath by the slot receiver. We can't see the actual receiver running his route here (a third of the screen is empty backfield so they could center the snap) but you can see everyone else processing events.

There's a replay but it doesn't show anything either. What we should see is some kind of communication between Johnson and Paige as the X receiver breaks inside and Johnson stays with him, with Paige signifying he has the slot in man. When the receiver this is going to and the guys covering him reappear on the screen things look not great. Everybody seems to have some kind of excuse.

Paige wiped out the slot receiver; he is exempted from blame. Barrett had a real job to do. There are coverages where Colson should be deep enough to take this away but I don't fault him for treating the RB as a threat on 1st & 10. This is on the three guys in deep coverage.

The MOST AT FAULT is Keon Sabb. I have some sympathy because it's 28-0 and the ONE THING that Sabb cannot do is allow a receiver to get behind him. But zone coverage is not about castling up like Stephen of Blois. By the time Washington stemmed his route inside, Sabb should have identified that there are only two receivers in the pattern, only one that could be heading into his zone, and only one area he could be running towards. This is a sliding scale—the more Sabb comes down, the more the more the receiver has to bend his route down to get open. When the receiver is catching it 20 yards downfield, and the free safety is still 5 yards back, the free safety has given up too much space.

That doesn't exonerate the cornerbacks, however. This is Advanced Cover 3 stuff we're in now, the part where you learn when and how you are supposed to leave your zone. The rule there is you cannot abandon your post without letting someone know they have to stay with their guy, and before that rule is the rule that you cannot abandon a receiver without passing him off to someone. Meaning Johnson should still be on this guy's hip, and Sabb should be hammering down, if not intercepting.

As for Wallace, the third rule is "Find Work." There is nobody threatening his side of the field, there is no coverage underneath, and there's nobody else who could possibly take away the inside leverage of this receiver. As soon as Wallace dropped and found neither tight end releasing, he needed to look up the receiver coming from the other side of the formation and get on his horse.

Again, it was 28-0 at the beginning of the 3rd quarter, and Nebraska ended up not scoring on this drive. A lot of these guys are just returning to action off injury. We don't need to dwell on this too hard. But now that our opponents saw what Haarberg and his weapons could do against Michigan's favorite zone coverage, it's a good bet we'll see it tested more in the weeks to come. While our secondary does the same, hopefully this will help you figure out what's going on.