Technical Football - Defense

Modern football fans are smart, and they keep getting smarter. Most people who watch football on a regular basis know what you’re talking about when you refer to a blitz, or to play action, or to a nickel defense. Commentators are going more in depth with their analysis every year, and the growth of internet blogs like this one has made it easier for fans to find in depth analysis. But there is still so much more about football out there, so much that even I don’t fully understand. This is a beautifully complex game, with nuances of technique and scheme that most fans aren’t aware of. So strap yourselves in as I take you on a highly technical tour of NFL defenses.

Note: As I said above, I don’t know everything. I never played football above a high school level, and several of the things I’m discussing below were never handled in my high school’s defense. It is very possible that some of my readers know more than me on these topics. If I’m wrong about something, feel free to leave a comment so I can correct it. I would love nothing more than to learn even more about football.

Linemen Positioning

The terminology for the positioning of defensive linemen has been around in football for decades, but it has only recently become common in the vocabulary of casual football fans. It is a fairly straightforward numbering scheme, shown the diagram below. The numbers increase out in a mirrored pattern from the center. The even numbers represent a defensive player lining directly in front of an offensive lineman—0 for the center, 2 for a guard, 4 for a tackle, and 6 for a tight end (if present.) The odd numbers fill in the gaps in between, though they technically refer to the outside shoulders of the respective linemen. As you can see, the numbers get a little messed up out around the edge, but on the interior it is mostly easy to figure out. Teams sometimes focus on finer details and will add the letter “i” to an even number to indicate the inside shoulder of an offensive linemen.

 

This terminology has been used in several contexts over the past few years. The most common is when describing the smaller, quicker defensive tackle in a 4-3 scheme. This defensive tackle is commonly known as “the 3-technique” since that is where he lines up in most normal alignments. Another common usage is when discussing a defensive end in the “Wide 9” position. As the name suggests, this indicates an end lining up far outside the tackle box. This offers a lot of advantages as a pass rusher, but it takes the ends out of the run game, opening up a massive lane for backs to run through. To play this sort of defense a team needs extremely stout linebackers, and it is normally used only in obvious passing situations.

One Gap

There are two main techniques employed by defensive linemen. The first and simplest of these is “one gapping.” A one gap scheme is all about pressure, relying on a defensive lineman to control a single gap by penetrating into the backfield. Linemen in this scheme are usually required to be explosive off the ball and to know how to disengage with blockers off initial contact. They are typically smaller and quicker than linemen who engage with blockers. Most of the linemen who consistently make plays in the backfield do so running a one gap scheme, allowing them the freedom to be aggressive and use their speed to shoot past an offensive lineman.

As you would expect, one gapping has its strengths and weaknesses. It can blow up traditional running schemes, penetration often making it impossible for backside linemen to pull around and contribute to the play. But it can cause problems against a zone running scheme, where blockers are perfectly content to let a defender run himself out of the play to give the runner an open lane to cut through. The one major advantage one gapping offers is against the pass, where penetrating defensive linemen can present quick pressure in the face of the quarterback. Edge pressure causes plenty of problems, but pressure directly in front of the quarterback can be even worse, giving him no time to make decisions and preventing him from being able to see downfield.

Two Gap

Two gapping is essentially the opposite of one gapping. In this scheme a defensive lineman is responsible for both the gaps on either side of him, and it is up to him to prevent the blockers from pushing him in a way that he can’t engage with a runner coming through either gap. He needs to use his size and his hands to establish control off the snap of the ball, standing the opposing lineman up and trying to push him into the backfield rather than trying to run around him. If he can gain proper control, he should be able to cast the blocker aside in either direction once he knows where the play is going.

Two gapping is what most people think of when they imagine defensive linemen, particularly defensive tackles. It requires someone who is big and stout (aka fat) to hold his ground and to allow the linebackers to scrape through the holes. It prevents the defensive linemen from making many plays, but it allows for a more cohesive, technically sound defense. It doesn’t provide much in the way of a pass rush, but the best defensive tackles can shove linemen back to collapse the pocket, giving the quarterback less room to escape from the edge rushers.

Stunt

There is another important technique used by the defensive front that I need to bring up, and that is stunting. A stunt is a called play intended to confuse an offense’s blocking scheme by switching the responsibilities of the defenders. The simplest form of a stunt is a cross, as shown in the image below. One lineman—in this case the defensive end—will crash hard across the blocker beside him, shooting into the gap between him and the defensive tackle. His goal is to draw the blocker ahead of him towards this gap while the tackle loops around and races through the open hole. The lineman responsible for the defensive tackle won’t be able to fight through the muddle, and unless his teammate can recognize and make the switch the defensive tackle will have a clear lane into the backfield. If he’s smart about it, the defensive end can even get away with grabbing hold of the outside offensive lineman to prevent him from sliding out and picking up the defensive tackle.

There are many varieties of stunts between the line and the linebackers. A crashing defensive linemen will often try to occupy two blockers while a linebacker blitzes in behind him. Stunts are effective against either the run or the pass, though they can also create easy leverage for an offensive lineman to use in the running game. They are better off used by teams without elite defensive linemen, who struggle to win individual matchups. If at all possible, teams are probably better off just letting their defensive linemen play the gaps in front of him.

3-4 vs 4-3

There has been a lot made about the differences in defensive schemes. Whenever a team struggles on defense, they usually bring in a new coach who promises a switch to a new alignment, exciting fans over all the possibilities. In truth, there is very little functional difference in schemes any longer. Traditionally, the 3-4 defense asked its defensive linemen to play primarily as two gappers, leaving its linebackers free to make more plays. But as the passing game has grown, 3-4 teams have begun to ask for more penetration from their defensive linemen, leading to the development of playmaking 3-4 ends like JJ Watt and Muhammad Wilkerson. And now that teams play most of their snaps with nickel personnel both schemes end up looking a lot alike.

Here’s Washington, a 3-4 team in the nickel.

And here’s Seattle, a 4-3 team in the nickel. See the difference?

When going to the nickel, a 4-3 team normally takes a linebacker off the field. When going to the nickel, a 3-4 team normally takes a defensive lineman off the field and moves their edge linebackers up onto the line. The only difference is whether the outside players go down into a 3-point stance or remain standing in a 2-point stance. So the next time you hear someone freaking out about the change from a 4-3 to a 3-4 or vice versa, try not to laugh too hard.

Zone Blitz

Blitzes have been around since the beginning of football, and most casual fans understand how they work. At the snap of the ball one of the linebackers rushes towards the line of scrimmage, attempting to shoot into the backfield to disrupt the play. Normally linebackers are supposed to read and react, but on blitzes they become aggressors like the linemen in front of them. Blitzes are useful for creating pressure on the quarterback and for breaking down the blocking scheme of a running game.

There is one major downside to blitzing on a pass play. Bringing an extra rusher means one fewer man in coverage, and for a team that wants to play a zone coverage scheme this puts an extra burden on every defender on the field. No offensive line can hold against a blitz indefinitely, but if they can weather the initial rush the quarterback usually has time to find a hole in the zone. Normally teams try to avoid this by playing man coverage, but in the past couple decades teams have found a way to disrupt pass protection without sacrificing the ability to play zone.

The sneaky secret behind a zone blitz is that it often isn’t technically a blitz. Like a normal blitz, one of the linebackers will rush into the backfield at the snap of the ball, leaving the other defenders behind him to play in coverage. But unlike on a normal blitz, on a zone blitz one of the defensive lineman will not rush the passer. Instead he will drop back into coverage, filling the zone that would normally be taken by the linebacker. The decrease in coverage ability is made up for by the confusion sown by the presence of the extra rusher and the man dropping into coverage where the quarterback isn’t expecting him, leading to plays like the one below.

Coverages

There are three primary categories of coverage schemes, all with names that make it pretty clear what they are. The number describes how many zones the deep portion of the field is split into, zones usually patrolled by safeties or cornerbacks. I don’t have the knowledge or the space to go into the full details of the coverages, so I will instead focus on the three largest blanket categories. Each of these is just one part of a coverage scheme, and they can all be played with varying schemes in the underneath portions of the field.

Cover 1

Cover 1 is the most popular coverage currently used in the NFL. A single safety will sit in the deep middle of the field, reading the quarterback to decide how to take away the top half of the defense. This frees a team’s second safety to drop down into the box for run support or to bounce outside to match up with a receiver in the slot. Cover 1 normally works best with man coverage underneath. Dividing the field into zones can take away almost every passing lane underneath, but there are very few safeties who can cover sideline to sideline in the deep zone. Most teams are better off matching up man to man across the board, relying on the single safety as a backup option in case the receiver beats his man deep.

Cover 2

Cover 2 is the most varied of all the coverage schemes. It is possible to play with either man or zone coverage underneath, and it is often used when a defense wants to try to disguise what it is doing from the quarterback. It offers plenty of protection in case of breakdowns, but it doesn’t take too many defenders away from the shorter portions of the field.

The scheme most commonly associated with Cover 2 is one that has fallen out of favor in recent years: the Tampa 2. Spread through the NFL by Tony Dungy and his assistants, it uses two safeties deep to patrol the outside of the fields while the cornerbacks sit in the flats to take away quick passes. The weaknesses of this scheme are down the middle of the field between the two safeties and on the sidelines in the window between the cornerbacks and the safeties. Ten years ago this was the most popular and most successful system in the league, but offenses have adapted to attack these vulnerabilities, leading to a trend towards more man coverage. Plenty of teams still use Cover 2, but they use it in a different way than they did a decade ago.

Cover 3

By now you can see the pattern. Cover 3 divides the field into three deep zones, usually handled either by a pair of cornerbacks and a safety—leaving the other safety free to roam—or by a single cornerback who rotates back to cover beside the two safeties. It is very difficult to complete deep passes against this defense, short of sending four receivers all running down the field together (which is actually a far better play than you would think.) Most teams that use this scheme employ a zone underneath. Playing man to man would leave only three defenders available to rush the passer, though teams sometimes still send four if they aren’t worried about the running back leaking out of the backfield.

Seattle’s Cover 3

There are countless variations to the basic coverage schemes I listed above, but Seattle’s version of the Cover 3 is one that I want to bring particular attention to. Seattle’s dominance on defense owes a lot to the fantastic players that make up that side of the ball, but just as much credit needs to go to their scheme, one of the most innovative and inimitable in the NFL. Their primary defense is a form of Cover 3, but they have enhanced it by playing press coverage with their outside cornerbacks before asking them to drop into deep zones. This takes away many of the quick passes to the outside that teams commonly use to exploit Cover 3 defenses, giving their linebackers additional time to drop into the flats while the cornerbacks float back into the deep corners.

This scheme is very difficult to beat, but it only works because of the discipline and athleticism of the players in it. Seattle has one of the most athletic linebacker corps in the game, allowing them to keep their linebackers in the box without leaving themselves vulnerable in the flats. The length and athleticism of their cornerbacks makes it easier to play press coverage and to recover when a receiver manages to slip the initial press. Even when one of their cornerbacks is beaten deep, the window for a quarterback to throw the ball over their outstretched arms is very small. And most importantly, they have the best cover safety in the game in Earl Thomas. Thomas is fast and smart, and he’s been coached up by Pete Carroll, who has been known for decades as one of the best defensive back coaches in football. Other teams are now implementing parts of this scheme into their defense, but it is highly unlikely that any will be able to replicate Seattle’s success.