Cal's Coverage Problems

Pass coverage is the hot-button issue for our team this season, so I want to keep chipping away at how it's supposed to work and the kinds of things that can go wrong.  This post will look more in depth at our Cover-4 package, the key responsibilities within it, and the things that can go wrong.

In my post on the Arizona game I looked at some routes that gave us trouble, and talked about the reasons that those routes are tough to double team if you can't match up personnel-wise. That post looked primarily at fades and slants, routes that you really want to be able to stop at least 50% of the time if you're playing them one-on-one. In any zone coverage most routes are defended by a combination of players, however. When one member of that combination doesn't do what they need to do, they can make someone else look bad. In zone, the guy closest to the ball isn't always the one who screwed up. To really understand what's going on with our pass defense, we need to look at the subtle ways in which zone defenders are supposed to help each other out so that no one gets left hanging.  This is a mega post with lots of diagrams and video, but I think it also has a few small but significant bits of information that you can translate immediately into your live game watching.

CB Play

Although this post won't focus on the CB's, I should probably start with them, since the techniques of the LB's and safeties often have an impact on what the CB's do and vice versa. Our CB's play with a few techniques depending on the precise Cover-4 variant that they're playing. One is to press their receiver. We're going to do this from a heads up or slight inside alignment, which should let us play the slant aggressively. We aren't often playing true man from the press in Cover-4, because we won't chase the WR all over the field. A pressing CB is mostly concerned with the 3-step quick passing game and the sideline fade, and will pass off shallow inside releases to the LB's.

There are a few things that are always important about playing press. The first is that no matter what, the CB needs to get a good jam on the WR. This is absolutely crucial. It doesn't always look like much, but the way to tell if you're getting a good jam is if the WR's shoulders turn toward the sidelines. Beyond that, the more the jam can slow the receiver down or force him off of his path, the better. This is how you disrupt the timing between a WR and a QB, and how you keep from getting burned. On a slant, you want to deny the WR an inside release and force him to fight through you to run his route. On the fade, you want to force him to bubble out toward the sideline as much as possible. The WR wants to run downfield in as direct a way as possible, leaving several yards between himself and the sideline:

It's a little hard to visualize in 2D, but imagine that the CB is running maybe half a step behind the WR in this picture. The QB is going to float the ball over the WR's outside shoulder. This means that the WR's body will be between the ball and the CB, making it very difficult to make a play on the ball. As the ball comes down the WR can lean into the CB and then push off a bit (with his body, not his hands) to the sidelines to get some separation and make an easy catch in space. This gives the QB some leeway. If the ball's underthrown a bit, the WR can slow down. The CB isn't going to run past him on an underthrown ball, so the WR can control the speed at which he and the DB are running while keeping his body between the DB and the ball. The QB can put some air under it and everything should be OK. Things are different with a good aggressive jam:

If the CB can get his hands on the WR and jam him up, he forces him to go farther toward the sidelines than he wants to. Now there is no space over the WR's outside shoulder for the QB to float the ball into. Even if the WR gets a step or two on the CB, the QB basically has to put the ball right on the money. If it's underthrown, the CB will probably intercept it, or at least it'll be a jump ball. If a QB misses a throw but the WR and CB are practically all the way to the sidelines, that's not necessarily the QB missing, but rather it's great press technique by the CB making the throw difficult. If a WR catches a fade several yards from the sidelines, that's on the CB for making the throw way too easy. That'll be a common theme throughout the post. You don't always have to have crazy tight coverage, especially in a zone. What you do need to do is a number of subtle things that make the throw tougher.  The more you can affect throws, the more incompletions you'll produce.  Right now we aren't doing enough of those things.

Aside from pressing, the other option for the CB in Cover-4 is to play off. In this situation, he'll be playing at maybe 7 yards off the LOS with either inside or outside leverage. His leverage will often depend on the WR's split. Remember, even when we're pressing Cover-4 is ultimately a zone coverage. The CB is only responsible for his WR in the 3-step passing game (hitches, slants), or on anything outside or straight downfield (outs, fades, some posts). If his WR takes a shallow inside release, he gets passed off to the LB's. With that in mind, let's look at a few WR splits:

Here the WR is taking a pretty narrow split to the QB, so the CB is playing him with outside leverage. Keep this in mind: WR's always take the splits that they do for a reason. If the WR's coming in tighter, what are the reasons? Well, he could be doing this to run some sort of shallow or intermediate crossing route. If that's the case, it's not the CB's problem, because he has all that help inside from his LB's and safeties. The other reason a WR might take a tight split is to get himself more space to run an out or a corner route. These are the routes that the CB has no help against, so he plays the WR with outside leverage to take them away. If the CB is playing with outside leverage like this and gets beat on a corner route, he screwed up. If he gets beat inside on a post, that's either a schematic loss by the DC or a failure by his help player, depending on exactly what the call is. If the WR takes a wider split, then the CB will probably play him with inside leverage:

Here the WR is split outside the numbers. Once again, he's doing this for a reason. Threats here are the sideline fade and the post route. The CB will, accordingly, play with inside leverage to take away the post, and will play the sideline fade much as described above in my paragraph on playing press. He obviously won't be pressing (because we're talking about off coverage now), but he's still trying to force that WR to the sideline.

OLB's and Safeties

That takes care of the common options outside. Inside is where things get really interesting, though, and that's where you should look if you want to see what adjustments we're making throughout the game. In general, we're going to play with a six-man box as much as possible. This is going to divide our coverage into two halves:

Remember that we want to have six men in the box. This means that we can remove one LB to help in coverage, but the other two have to stay in as run defenders. This leads to an inherent imbalance in our coverage. On the left of the diagram we see that the CB, FS, and SLB are playing 3-on-2 against the X and H receivers. On the right of the diagram, the CB and SS are playing 2-on-2 over the Z and Y WR's. We'll call the 3-on-2 side the “Read” side of the coverage, and the 2-on-2 side the “Away” side of the coverage. We'll usually put the read side to the wide side of the field, where there's more space and, therefore, a greater need for that third pass defender.

We'll start with the read side, which will be comprised of the CB, safety, and either an OLB or a nickel back. All kinds of Cover-4 are at their best and simplest if both WR's run straight down the field. If this happens, the CB and safety take their WR's man-on-man:

That's how this particular combination of WR routes will be covered against every Cover-4 variation, so there's no mystery or complexity here. The trick comes when you're talking about the third player, or “help player” in that coverage surface, who is going to be the OLB or nickle back. Our starter call from base 4-3 personnel against the spread is “Read.” Let's start with the rules for the help player (SLB/NB). He lines up off the line of scrimmage and inside the inside WR. His job is, first and foremost, to stay inside that guy and to deny the middle of the field to him. If that inside WR breaks outside then the help player becomes a curl/flat defender and expands with him/watches for additional flat threats. These rules show us how this is set up to take away a slant:

That's the simplest of his responsibilities. As the result of his inside position, however, it's also his job to protect the safety, who is responsible for the inside receiver if he goes deep. If the inside WR goes deep, the SLB has to stay with him and inside of him, denying him the deep middle of the field until he passes him off to the safety at around 12 yards deep:

This stage is critical, because if you look at the diagram you'll see that the FS is playing in a TON of open space. As it is he's responsible for covering a slot receiver deep, so he's already probably at a disadvantage in terms of athleticism. The SLB has to make it impossible for the WR to cut inside to the middle of the field so that the safety can cover things vertical and to the outside. If he doesn't do this, he's really hanging his safety out to dry:

That safety will have a really tough time staying on top of the WR to defend against a potential go route while also being able to play tight on him on a potential post route and being in position to defend him on the corner route to the outside. It's just too difficult for the safety to be able to defend all those possible breaks at once. The SLB has to delay the inside breaking routes to give his safety a chance.  Here's a video. The first play (looped three times) shows the OLB's playing inside their WR's and passing them off to the safeties. The second play shows what can happen if the OLB doesn't deny the inside release to his WR.

 

So the help player is lined up inside the WR and denies him an inside release, both on the slant and on deeper routes (on a shallow cross, depending on gameplan and other factors, he can either wall him, pass him off to the next LB inside, or run with him). The big problem with this alignment is going to be to the outside, and a lot of you've probably noticed us giving up some out routes:

 That's a tough draw for a LB vs. a slot receiver. This is where the read element of “Read” coverage comes in. To make sure that the flat gets defended, the CB will be “reading” the inside receiver (even though he's lined up over the outside receiver). If the inside receiver runs vertical, than the CB covers his guy man-to-man on anything outside or down the field. Easy. If, on the other hand, the inside receiver breaks to the outside, then the CB will come off of his man to cover the flat, and the FS will work over the top of the outside WR. This works best if the CB plays with outside leverage:

 The CB can stay outside of his WR and keep him from quickly getting to the sidelines, making it easier for the safety to get over the top of him. Once he sees the inside receiver breaking to the outside, he comes off his man and covers the flat. If he fails to see this and jump the flat route, he's going to make his SLB look really slow and bad, but the inside receiver isn't covered by one defender. Instead, different defenders are covering different routes. The SLB defends him on the slant and delays him on the post, the CB defends him on the out route, and the safety defends him on the go route over the top. Here's a video of Walker limiting the out pretty well:

 By having the CB come off to cover the inside receiver on any out-breaking routes, we also have a built in answer to the post-wheel combination:

 

 The CB will see the inside receiver break outside, and so will come off his man to cover the flat. When the inside receiver turns up-field for the wheel route, the CB simply stays with him. The safety, who has also seen the inside WR break to the outside, is now getting width and depth over the outside WR, who is coming straight toward him on the post route. Easy.

There's one more route combination that we should discuss in the context of “read,” and that is the smash concept, a concept where the outside receiver runs a short hitch or out and the inside receiver runs a corner route behind him:

 This is the main combination where we don't have great leverage. As we know by now, the CB is reading the inside receiver, but since the inside receiver's release is vertical, he's not going to come off his man. The outside WR runs a 5-yard hitch or something similar, and the CB sticks with him. The SLB, being lined up inside the inside WR, is only able to deny him inside breaking routes. There's no one obstructing that WR's path to the outside. This leaves the safety all alone trying to cover the corner route, which is tough. Once again, though, we should be covering this route with a combination of players:

The CB isn't taught to stick with his receiver no matter what. If his receiver stops short, the CB will continue dropping. The hitch isn't a big problem, but a potential corner route is, so he'll continue dropping to 10-12 yards. That way, if the QB wants to throw the corner route, he has to put air under the ball, giving the safety more time to recover and make the play. If and only if the QB commits his eyes and shoulders to throwing the hitch, the CB will rally to the short throw and make the tackle for minimal gain. This is an acceptable outcome, because if he doesn't sink under the potential corner route, he's going to make the safety look slow and awful, since that's a match-up that the safety will have a hard time winning without help.  Here's a video with two plays, looped three times each.  The first shows the CB affecting the throw significantly and leading to an incompletion, the second shows a play where the throw isn't affected at all:

 

In the preceding discussion, you'll notice that on some of these concepts we're mostly content with giving up short completions to the flat.  We're taking away the deep stuff first, and rallying to underneath throws.  That's not what we do all the time, though.  While Read has a lot of answers built in, there are times when you need to adjust. What if, for instance, you want to double the outside WR, or tighten up coverage on routes in the flat? A slight tweak in personnel and alignment gets you into, Robber, a different set of coverage rules:

You can play this from several alignments and personnel groupings, and we do. The CB and NB can either press or play off, and you can also play it with the SLB instead of a NB. The key is that the help player (SLB/NB) is now going to press or play outside leverage on the inside WR. The key difference between Robber and Read is that in Robber the help player will carry the inside WR outside and on the wheel route, meaning that the CB never has to come off of the outside WR. Another difference is that, because of the help player's outside leverage on the inside WR, he's not in a position to deny an inside release on the post route. He is in position to delay an outside release on the corner route, though, so the safety can worry more about covering the post.

One of the ultimate benefits of Robber is that we're able to get a double team on the outside WR much more easily. Here's the out concept that we saw above, and the way that Robber is going to defend it as opposed to Read:

The CB is no longer reading the inside WR, because he's not responsible for him on out-breaking patterns. When the outside WR goes deep, the CB simply stays with him. When the inside WR breaks outside, he's no longer an immediate vertical threat to the safety, so the safety gets width and depth on the outside WR. Because the CB no longer has to be a flat defender, in Robber he's also going to be better able to press his WR, both because he might get help over the top and because he doesn't have to worry about the inside WR at all. He could also play off and with outside leverage:

This will help to defend the sideline from the outside WR, and will let the CB play outside any go routes or posts, forcing his man inside to the FS.  Here's a video of robber coverage from the WSU game.  The inside WR runs a dig, but you can see at the bottom of the screen that the nickel back is playing with outside leverage, denying the out route and the corner route to his man.  When the inside WR doesn't go vertical, we get a nice double team on the outside WR, forcing an overthrow by Halliday:

 This comparison of Robber and Read is illustrative, because neither is a called double coverage, but they will both give you double coverage on certain receivers on certain routes/concepts. If you're getting killed by a specific WR on the post, for instance, you can get into a call like Robber that will double him on the post, but that won't waste a defender doubling him if he runs something like a slant, hitch, bubble screen, etc. You're doubling routes, not receivers.

To round this off, I should talk about the away side a little bit. If you want to keep six defenders in the box, you're probably left looking at a “Man” call, which is exactly what it sounds like:

The SS and CB cover their receivers man to man, and you've basically got a Cover-0 shell going. If you don't care about keeping 6 in the box, you can play any of the combinations that you did on the other side. Here we're playing “read” to the short side (the right side of the diagram):

When you're talking about coverage into the short side of the field, you might want a better call for taking away the flat, since the throw for the QB is pretty short. Something you'll see a lot into the short side of the field is just a simple Cover-2 shell:

  This coverage actually gives you the exact same assignments as Read would against this concept.  The difference here is that the CB, instead of dropping with the outside WR and rallying up to the out route, will squat in the flat and play the out route head-on.  The safety plays as a deep ½ defender. It's also possible to play either the Read or Cover-2 variants from a 6-man box, so long as you do it to the short side of the field:

 If you choose to play it this way the assignments will be the same as for Read or whatever, but you're just conceding that you might be a little slow getting the WLB out to wall off the inside WR.  This becomes especially true if there's any kind of playaction fake that holds the WLB from getting to his pass assignment.

Those give you some of our basic options from a Cover-4 shell.  So, just to recap, how can you turn all of this into something useful for watching a game?  As discussed in this post, the most important players for determining coverage responsibilities will be the OLB's/NB's. Their alignment will give you everything you need to know about the coverage variant that we're playing, and their leverage will tell you what we're trying to take away. Next time you're worried about a slant, look for those guys. Next time you're worried about an out, look for those guys. If you understand where they are and what they're trying to take away, you'll understand what everyone else needs to do to cover the rest.  

Discussion thread: http://bearinsider.com/forums/showthread.php?87242-Understanding-Our-Coverage-Problems&p=842379322#post842379322