Sorry this one's short, since I'm neck deep in the HTTV editorial right now. When we did the Marlin Q&A I shot him a question over email after the fact about his favorite type of defense. The answer I got back was very detailed, and mostly Greek to anyone who hasn't immersed themselves in it. I also thought it made a great snapshot answer to the question of what's the difference between college defense and pro/Alabama defense.
What's your favorite type of defense/base formation? Is there one that's more fun to play in and another that you think is the most effective, or are those one and the same?
My favorite type of defense is the 4-3 zone blitz with a mix of cov 4 and cov 2. My favorite coverage was one named Rolex, a mix of cov 4 and 2. DBs must read the number 2 receiver in order to know which cov to play, if 2 goes to the flat, outside corner comes off one and plays cov 2 while the safety pushes over the top of #1. If #2 goes vertical instead of to the flat, the safety takes #2 and the corner stays on #1 playing quarters cov.
Glossary (skip this part if you're already comfy with football terms)
4-3: The 4-3 you know: four linemen and three linebackers. Because the NFL plays with so many different fronts, specifying the base shift isn't necessary—they're going to align to what the offense shows and change it up three times before the snap to confuse the offense.
Zone blitz: Credited to the '71 Dolphins and popularized by LeBeau with the Bengals and Steelers. All it really means is dropping guys you'd expect to pass rush into coverage and blitzing from one of the guys you'd expect to be playing coverage. In a 4-3 defense it usually means a defensive end is in dropping into coverage and a linebacker or safety is blitzing. Granted your DEs are not going to be Ed Reed out there but it's effective because you screw up the OL's blocking assignments and you can get some quick picks from quarterbacks trained to throw in the direction of the extra rusher.
a typical cover-2 zone blitz
Cover 4 and Cover 2: Two basic defensive schemes for playing zone defense:
As you can see by the size and shape of the coverage zones, they have different strengths and weaknesses. Cover 2 is strong against short passing and is effective against the run because the linebackers don't have to go very far and the corners can keep that edge. It's weak to either side of the safeties, beaten by abusing the MLB deep or the spot on the sideline over the corner's head. Common routes to beat Cover 2 are seams, four-verts, and posts, which put receivers on either side of the safety's zone, or going high-low on the cornerback, making him pick between receivers running routes both under and over him.
Cover 4, also called "Quarters" is strong where Cover 2 is weak, and vice versa. You attack it by attacking the flat, for example with stop routes or making a linebacker carry a receiver/tight end to one side of his zone and having a back roll into the spot just vacated. You also can attack Cover 4 by running into it, but because the coverage just went back to normal for those safeties, and because the NFL has guys like Marlin, and Polamalu, and Ed Reed available to them, some coaches use this opportunity to line up one or two safeties in the box as supplemental run stoppers, trusting he'd have the speed to get back to a deep zone. Ohio State and Virginia Tech do a lot of this. The base quarters play is this:
The Flat: You should know this but it's the area between the hash marks and the sidelines within 10 yards of the line of scrimmage.
1 receiver, 2 receiver: Lots of coaches have different terms for the different receivers in any given formation, and defensive coaches have their own sets again for better kenning. In this terminology throw out all the stuff about slots and Y's and split ends versus flankers, and just think of the No.1 receiver as the outside guy.
Cover 2 and Cover 4 both split the field in half, so in the defensive back's mind he just needs to be watching to see what the receivers are doing on his side, hence the plural 1's and 2's.
High-Low: He didn't say that but it's what this play is trying to prevent. The cornerback on the right of this gif is getting high-low'ed:
In this case the corner plays it safe and decides to stay with the receiver running a flag to the top of the corner's zone, effectively forcing the corner to play a Cover 4 zone and abandon his Cover 2 zone, where there's now a tight end hanging out with a whole lot of nitrogen. Boom: high-low'ed.
If you look at left side of the above-gif'ed play, you can see they're running the other thing that beats Cover-2, putting the free safety in a bad choice (and requiring the cornerback to turn and carry the receiver out of his zone). If you start covering the flat and leave the #1 receiver to the safety, the offense can punish you deep and down the middle. Here the free safety was put in a bad choice between taking the tight end who's already behind the linebackers or a receiver who's behind his corner's zone. Boom: vert'ed.
But what if you could play Cover-4 when they try to verts you, and stay in your Cover-2 zone when they try to hit you in the flat?
This is Rolex
purple means it's a read
The point of this play is to take away one of the methods of beating Cover 2—going high-low on the cornerback—without opening something else up by having the safety and corner read the #2 receiver (for ease I've made this the tight end) and adjust accordingly.
In the example above, if Y goes into the flat, then the cornerback lets the receiver go and covers the flat, and the safety knows he is responsible for that receiver (who you're expecting to head out to corner). If the Y is running a vertical route the corner and safety play a Cover 4.
This Isn't Cover 4 or Cover 2
If you watch the linebackers' zones, it looks like a Cover 2, since the outside guys aren't covering the flats. From the offense's standpoint, the whole thing is playing havoc with the keys you've been drilled on since your first snap: the zone blitz means there's coverage in the direction the pressure is coming from, and though you recognize Cover 2 zones in the first few seconds of the play, when you go to throw the pass that's supposed to beat Cover 2, there's a cornerback or safety playing it super-aggressively.
How to Beat It
It's a changeup, not a complete defense. Marlin didn't say what they do if the #2 receiver goes on a slant inside or something, but I think that plays right into the teeth of the defense; just double up the #1. I am confused about how they deal with the opposite high-low method:
…since the corner's read is going to drop him into Cover 4—perfect spot to intercept a ball to #2 but who's got #1 now? My guess is he just plays quarters with the linebacker (or in this case the SDE), who has responsibility for the flat. Also the SS is playing quarters so he's got his ears back.
Best I could find after watching lots of tape (Marlin failed to mention it was an Eagles defense until after I'd watched a lot of 2007 Colts). The #2 receiver stayed in to block, and the corner reads the backfield to be sure there isn't an RB trickling out into the flat, then leaps into Cover 4. The LBs are playing Cover 2. Another from that same guy.
Can we try this?
Mattison certainly played with this kinda stuff with the Ravens. But this year we're going to have at least one untrained safety, and the corners have about a year and a half of experience between the two starters. The thing about this play is it requires several defenders all to make the correct read and react to it quickly. It's the kind of advanced stuff that an NFL defense can install and practice until it's second-nature, but seems like a hard thing to get a young secondary to do. In the future, projecting that a handful of the defensive back recruits do work out, yeah I absolutely see Michigan trying stuff like this. Mattison loves his zone blitzes, and you could see in 2011 and last year that he wanted to put some more quarters and mixed coverage stuff in.