Thursday, May 24, 2012

The Zone Blitz

(And eventually, here it is. The fabled post about the Zone blitz.)

It's been such a long time since I last did a post with diagrams. So refreshing to get back into some of the "x's and o's" of football. Just hope I can remember how many diagrams I'm allowed to put in and don't run over the limit. That's before we even get into the issues about whether the new blogger interface will permit me to put pictures in? We'll find out I guess.

So in this post I want to take a look at the zone blitz. We often here this name banded about in the footballing world, but what exactly is a zone blitz and why do teams use them?

Well first off it would be a good idea to look at the history of the zone blitz. Unfortunately, like most things in football, that could take years of research to finally sort through all the various claims made by people over the years who say they were the one that invented the zone blitz (or claimed a hefty hand in it). The only claim of any sort that seems to hold any strong, consensus merit, is that current Steelers defensive coordinator Dick LeBeau is responsible for popularizing the zone blitz among NFL teams, through his work with both the Bengals and Steelers.

That out of the way, just what is the zone blitz? To understand it we first need to look at the alternative, that being the man blitz.

The man blitz comes in two basic forms; "cover zero/0" and "cover one/1 - man free". Cover zero involves putting a defender man to man on every single one of the five eligible offensive receivers. The remaining six defenders are going after the quarterback! This is where we get the "zero" from, because there are zero deep defenders.

Cover one - Man Free, involves almost the same as cover zero, except one of the six blitzers is sacrificed in favour of a deep defender. He becomes the "one" in "cover one". The fact that the free safety is the logical choice for this role (and indeed almost always is chosen) gives us the "free", though I've heard disputes over this etymology with some saying that they were taught that "man free" meant for the outside coverage defenders to let their man run free down the sideline, but I have to say that seems like a rather bizarre interpretation if you ask me.

Regardless, below I've done a diagram of what a Cover 0 look, erm, looks like. The dotted lines indicate which receiver a defender is covering, while the solid black arrows pointed ominiously at the quarterback represent blitzing defenders;

Now the point of a man blitz is simple; it's a calculated gamble.

You're putting your coverage men in a tight spot by making each of them cover a receiver man to man, but that's compensated for by the extra pressure that you're bringing on the quarterback. You're hoping to either get a sack before he can release the ball, or to cause him to rush his throw such that he makes an error - either in judgement or with accuracy - and throws an incomplete pass, or better yet, an interception.

The key to cover zero is that if all five eligible receivers release into a pattern then that only leaves five offensive linemen to block six rushing defenders. Even if we assume perfect blocking by the offensive line that still means that someone is going to be coming through untouched for a free shot at the quarterback!

The downside of course is that there is no (zero) top cover by a deep safety. If our pass rushers don't get to the quarterback in time or he manages to make a quick and accurate throw, then there is nobody left between the receiver and the end zone. That's only going to end one way and it's not good for our defense. It also allows an alert quarterback to victimise certain corners who are matched up against his bigger, "target man" style receivers (like Larry Fitzgerald) by simply throwing up a jump ball.

That's the gamble you take; extra pressure versus the possibility of giving up a large gain.

The zone blitz is a way of trying to get the best of both worlds. You're bringing pressure on the quarterback while also playing a much safer coverage behind it, so that if the pressure fails to get home then your coverage men still have the opportunity to make a play, and failing that they are at least in a better position to try and bring down the eventual receiver before he reaches the end zone.

Zone blitzes also give the defensive coordinator a degree of flexibility. He can chose different combinations of rushers, perhaps opting for an overload blitz from one side, and he can also mix up the type of coverages he uses on the back end while still bringing the same number of rushers up front.

A basic example of this is demonstrated below;
With the Will and Sam backers rushing the quarterback that leaves the corners holding the 'curl/flat' zones to the outside, with Mike and Ted playing underneath across the middle, and the two safeties each taking a deep half of the field.

Here we're now able to bring five rushers while still keeping a relatively solid coverage scheme behind them. We're still looking to get after the quarterback with extra pressure, but at the same time we're in a little better shape if that fails. Perhaps just as important is that now if the quarterback panics under the pressure and throws a bad pass, our zone defenders will be looking right at him when he does it. They're better able to read and react, pouncing on any errant throw.

This also brings us to one of the trade offs when it comes to zone blitzing. Obviously you can see from the diagram above that the four underneath defenders are going to have a difficult time covering the width of the field between them, not helped by my budget diagram making skills, that have condensed the left side corners zone and given Mike a little bit too much room than he would actually be expected to cover in a real game.

Still, the point stands, there are some quite significant gaps between defenders. A good quarterback with time on his hand will pick a defense like this apart in short order, zinging passes through the wider gaps compared to a 5 underneath coverage that you would have if you only rushed four defenders.

Again it's a gamble, a sacrifice, a balancing act. We're trading slightly larger gaps in between the coverage defenders in favour getting an extra man into the pressure scheme to get after the quarterback. If the pressure pays off and the quarterback throws a bad pass then the wider gaps wont matter, and in some cases may actually result in a pick.

Now, "zone blitz" is a very broad term and the amount of variations of different pressures and coverages is quite vast. But even in that large soup of potential defenses there are a few stand out examples that are worth highlighting, which is precisely what we're going to do. There are two sub sets of the zone blitz that I want to highlight and they are; 1) a zone blitz with a dropping D-lineman and 2) the fire zone blitz.

Number one is an oddity that sees a defensive lineman drop out of the pass rush and instead back track into coverage. Once quite a rare sight in football, it's becoming increasingly common, especially so in 4-3 defenses that are looking for new ways to mix up their coverage schemes to keep themselves fresh and present new problems for quarterbacks.

Let's have a look at an example;
In this case the defensive end on the weak side is dropping out into zone coverage. The Will linebacker moves across to cover behind the pressure and we get a five man blitz from one side of the field. This is also a reasonable example of an overload blitz, as we have 5 rushers against 3 offensive linemen. The tight end might be kept into block, but generally he'll be out as a receiver. You're now relying on your two running backs to pick up the other two rushers, providing they are even both staying in for protection. If they are then you probably don't need me to tell you what happens when running backs try to routinely block fast moving linebackers.

As with all things football there ups and downs to this approach. The plus side is that you can surprise a quarterback and his protection scheme by doing something a little out of the blue. Having watched a whole bunch of tape where that left defensive end rushes every play, and having already seen maybe 20 plays that day where he did the same thing, it can come as quite a shock to a quarterback when he suddenly drops off into coverage. At the same time you have that strong over load blitz coming from the right.

The down side is that you've just put a six foot four, 270-280 pound man who is built for pass rushing out into space to try and cover a zone. Unless the ball happens to be thrown quite close to him, he's less likely to be able to make a play on it than a linebacker would. He's also inexperienced at playing coverage, so he may not get the correct depth or width for his assignment, leaving a big opening to be exploited.

Further more, because we're bringing an overload pressure from one side of the field that means we have to ask the Will linebacker to get across to cover. That takes time, and if the quarterback and the tight end are on the same page we may seem them execute a "hot" throw, where the tight end realises that heavy pressure is being brought from his side and thus stops running his route and instead turns immediately to look for a throw. If this happens, there is no chance that the Will linebacker will get across in time.

Again, and I'm sorry to keep repeating this, but it's a gamble. We're taking a chance with the coverage in the hope of creating a positive play with that overload pressure. It might be worth at this juncture pointing out that taking the odd gamble is actually quite healthy for a defensive coordinator (and offensive coordinators), as long as they understand the risks they are taking and take those chances in a somewhat measured manner. A calculated gamble based on the game situation and the opponent can reap huge rewards, while reckless gambling can often throw away a game that should otherwise have been perfectly winnable.

Moving on now we come to the final blitz that I want to touch on, and that's the Fire Zone blitz. The fire zone blitz is a relatively simple concept that comes in many variations and forms, but all share a commong theme; 5 pass rushers, 3 underneath zone defenders, and three deep zone defenders.

Here's what it looks like;

In the picture above you can see that we still have five rushers, but now the two cornerbacks drop off into deep zone coverages along with the free safety, each taking one deep third of the field. The Strong Safety comes down into a short zone underneath, the Mike linebacker stays in the middle and the Will linebacker goes out into the short zone to the side.

The benefit of this type of coverage is mainly that it a) it's quite unpredictable and b) it gives us good deep coverage. The unpredictability though is the main driver. Because we only need three underneath defenders we can be very flexible about who drops back and who rushes. Given that there are only three deep responsibilities and we have four defenders capable of covering those deep areas, one of them will nearly always be involved in the underneath coverage. That means we only have to strip two of the remaining front seven players to complete our coverage.

This also generally helps to explain why 3-4 teams are much more at home using the zone blitz than 4-3 teams. By replacing a slightly ungainly down lineman with a more lithe and agile linebacker it makes it a lot easier/safer to use schemes that require one of the wider men on the line of scrimmage to drop off.

There are also lots of novel ways to manipulate this scheme to best effect. Teams like the Green Bay Packers have become quite at home with dropping a defensive linemen back into the middle of their defense to cover that middle zone, allowing 3 of their linebackers to rush the quarterback (assuming the other is involved in the coverage). It can be quite a surprise for a quarterback to see a swathe of pressure coming right at him and then looking straight down the middle for a pass to the tight end, only to see a nose tackle suddenly come into your line of sight!

The disadvantages are that again you could be putting a defensive lineman, not ideally suited to the coverage role, into a coverage role. Also, with only three defenders underneath it means there are some gaping holes to be exploited. This is compounded by the fact that some of the underneath coverage men will be running at full tilt to get into position and thus are vulnerable to having passes thrown behind them where they will find it difficult to stop and do a 180 degree turn in time. Again, much relies on the added pressure and the surprise generated by the pass rush to confuse the quarterback into making a mistake.

So there we have it, the zone blitz. Not the most comprehensive article you'll ever see and maybe in the future I'll take a more in depth look at something like the fire zone, but as a primer it'll do. I hope you enjoyed it and can get some use out of it. If so then by all means pass this on to others, click one of the share buttons at the bottom, send it to a friend or just spread the word of mouth. I'd be very grateful.

As for future postings. Right now I have on my "to do list" two things, one being to go through and have a closer look at the third round draft picks, which is something I've already partially made a start on, and the other is to do an article about pass routes and how these can be adapted on the fly by receivers to avoid some of the problems with putting together offensive plays that have multiple concepts in them designed to beat multiple coverages.

At some point this off season I would also like to do a post about just what kind of things NFL teams do in training camp, specifically how they organise their time and how they break down their practices.

Until next time, enjoy the sunshine!

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