Sunday, August 31, 2014

Cal vs. Northwestern: TD's TD

I've spent a lot of time talking about our offense, but it doesn't exist in a vacuum. The plays that are called and the success that they have is largely dependant on what the defense is doing, so if you really want to understand the Bear Raid you need to understand the defenses that it faces. In this post we'll look more in depth at quarters coverage (Cover-4), and the way that we were able to break it on Trevor Davis' long TD reception against Northwestern. I think that the commentors got this right on the TV broadcast so the conclusion won't be a surprise, but this post will hopefully give a deeper understanding about why Northwestern was running what they were running, and will let you recognize this kind of thing for yourself when it happens in the future. Also, if you see some of the defensive stuff that I'm about to discuss happening in a game, you'll know what kind of plays we should be calling!


The Nature of the Spread
First, let's look at what kind of passing game the spread can accommodate that the I-formation can't. The mantra on TV broadcasts has always been about “speed in space” and “winning 1-on-1's” in the spread, but that really doesn't describe the spread passing game. It's not about getting 1-on-1's and requiring guys to break tackles (although that's where the explosive plays come from). At a much more fundamental level, its about stretching defenses by flooding zones with multiple receivers, making individual defenders wrong no matter who they cover. This is why the spread started with teams that had less talent than their competition (at least in its most recent incarnation; TCU was already spreading the field to win national championships in the 1930's: https://www.youtube.com/watch?v=ZGqcGHX3xjQ). Over the last decade spread concepts have become increasingly popular with more traditional powers because the concepts are sound schematically, so let's see exactly what kinds of challenges the spread poses for a defense.  Here's a basic spread formation:
 
We can compare this to a pro-I:
Both of these formations have a strong run tendency. I-formation teams will usually run to the TE (right in the I-formation diagram), and will be best at running to that side. They have more blockers over there, and that lets them do more. Shotgun-spread teams, on the other hand, are usually going to run in the direction away from where the back aligns (again, right in the spread diagram). This is because, when in the shotgun, the back already has to move to his right to get the ball from the QB. Changing directions for a run to the left would slow him down and make the play take longer to develop.

Against the I-formation, defenses can match this tendency by rotating their coverage toward the TE:
Now they have two DB's to the right of the diagram and one safety in the middle of the field, with only 1 DB to the left of the diagram. The I-formation also has a clear passing strength, because one side of the field has two receivers (the flanker (Z) and TE (Y)) while the other only has the split end (X). When the defense rotates their coverage toward the run strength, therefore, they're also rotating to the passing strength, so they can match the offense's strength with their own.

This is more problematic against the spread:

  
Here once again, the defense is rotating toward the run strength (the right side of the diagram). The problem is that, from the shotgun, the left side of the diagram can very quickly become the passing strength. The defense is rotating to the right side of the diagram, but the offense has three receivers to the left. On the concept in the diagram above, this creates a situation where X is able to run off the CB while the WLB is stuck in between F and H, who are creating a horizontal stretch in the curl and flat zones. It's not about making guys miss (at least to get the completion), because the WLB can't effectively cover both guys at once. The shotgun specifically helps with this situation because the back is aligned over the OT instead of behind the C and, on most pass plays, is closer to the LOS, letting him get into the route more quickly than a RB in the I-formation could. This is also why spread teams like fast, pass-catching RB's.  If the RB isn't a receiving threat here, the stretch becomes much less effective. 

The other benefit of the spread against a secondary rotation is this:
 
The spread (or really any 1-back formation) gives the offense the ability to run four receivers straight down the field. A secondary rotation, by definition, pulls one of the 4 DB's out of deep coverage and puts them into underneath coverage, so the offense has a 4-on-3 matchup deep, which is obviously a huge problem for the defense. In general, this is the kind of thing spread offenses can do especially well: because there are so many genuine receiving threats, with multiple receivers on each side of the formation, they can create all kinds of stretches on zone defenders and make it very, very difficult to cover everyone without going to man coverage.  Even when teams like tOSU and Oregon do pass, they're using these same kinds of concepts to spring guys open.

In short, the spread passing game and the nature of the basic spread formation strongly discourage defenses from rotating their coverage to one side of the field or the other. They need to play “balanced” coverages, with two DB's on each side of the formation if they want to match-up with all of the receiving threats on the field.

Quarters Coverage
For the reasons listed above, Quarters (Cover-4) is quickly becoming a default way to defend spread teams:
  
First of all, how can you recognize quarters from the stands or on TV? The obvious answer is that the DB's will be 4-across, but they won't always be at the same level so it's possible to confuse Cover-4 for Cover-2 or Cover-0. The best way to recognize Cover-4 is to look at the depth of the safeties and their movement at the snap. In Cover-2 the safeties will usually line up 12-15 yards deep, and at the snap their first movements will probably be to get depth and width, since they are the primary deep defenders and so must be able to stay over the top of a deep route by any receiver. In quarters, the safeties will line up 10-11 yards deep, and at the snap they'll stay still for a beat while they make their read. The CB's aren't necessarily a reliable indicator of the coverage, because within Cover-4, depending on the variant they could do anything from playing press-man and following their guy wherever he goes, to lining up 8 yards off the ball and bailing deep no matter what.  Also, the CB's on each side might be doing different things, so the CB's really don't tell you a lot.  No matter what coverage you're looking for, the safeties will always give you the information that you need (that's why QB's read them). They're also perhaps the best indicator of what's going on in the run game, if any blitzes are coming, etc., so they're really the best unit on the football field to understand well.

The most obvious advantage to Cover-4 is that you can easily defend 4-verticals. Your DB's line up over the four WR's, and everything's easy as can be. Another benefit is that in quarters, because the CB's are responsible for the outside receivers deep, the safeties can play closer to the LOS; because someone is already covering the outside receivers, the safeties' primary pass responsibility is to make sure that the inside receivers don't run straight past them, but other than that they can focus on defending other things (especially runs and screens). A good quarters team can get eight or even nine defenders involved against the run with good safety play. This is why quarters is often used against Oregon-style spread teams as well as Air Raid-style teams.

The big problem with quarters is that it is still vulnerable to underneath stretches in the spread passing game: 

Assuming that the FS and CB can't get involved underneath here (more on this below), the WLB has the exact same problem that he had in the rotated coverage discussed above. The big problem for quarters, and for defending the spread in general, is in taking away these underneath horizontal stretches. As the need to use quarters coverage has expanded with the rise of the spread, defenses have also gotten more sophisticated in their use of it, to the point that there are a significant number of tags and variants that teams can use to take away specific route combinations while still playing this nice, balanced coverage.

First, let's look in more depth at a Cover-4 variant that can't defend the passing play in the diagram above:
We can call this set of rules “Cover-4 Read.” On this variant the rules are as follows: The CB is in man-coverage on the #1receiver (X) unless he goes inside.  He can do this from a press alignment even better than he can from the off-alignment in the diagram above. The FS is reading the #2 receiver (H). If #2 pushes vertical, the FS covers him. If #2 doesn't, then the FS sits on the post and curl routes by #1 to help the CB. This means that when #1 goes deep and #2 doesn't, the FS becomes a deep defender, leaving the WLB stranded against F and H.

If a Cover-4 team is getting killed by the route concept in the diagram above, they might switch to “Cover-4 Combo.” This changes up the reads and rules for the DBs:
If #1 (X) and #2 (H) both go vertical, then the CB and FS simply cover them man-to-man, just as in Read. In Combo, however, the CB only drops with #1 vertical until he gets the flat threat. Meanwhile, when the FS sees that he isn't getting any #2 receiver vertical, he immediately gets width and depth to stay over the top of #1 (X). The CB takes F in the flat, the FS takes X deep, and the WLB only has to worry about H. This really becomes a more aggressive (from the safety's perspective) version of Cover-2. In Cover-2, as I mentioned above, the FS would have been aligned at 12-15 yards at the snap and would've gotten depth and width immediately, whereas in quarters he aligns at 10-11 yards deep (making him a better run defender) and only gets depth and width once he's made his read.

All of this gives you the knowledge that you need to break down Trevor Davis' long TD pass:

Here are some things that are good to look for if you want to speed up your own recognition while you watch games live, and to help to do your own immediate breakdown once a play's over: How deep is each safety at the snap, and where are they? Why does Northwestern have to use a coverage variant that puts the CB in the flat at the bottom of the screen? Using what we now know about quarters, why do the DB's at the top of the screen do what they do? Are there any other structural deficiencies in the way that Northwestern's defended this play? Bonus points to the first person to name the pass concept we're using here. Let me know what you see: http://bearinsider.com/forums/showthread.php?85803-Bear-Raid-Breakdown-TD-s-TD

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