There are two main defensive schemes in the NFL. These defensive schemes are defined by their front 7 alignment as either a 4-3 defense or a 3-4 defense. Within each scheme there are variations, such as 1-gap or 2-gap principles, or Cover 2/Tampa 2 zone secondaries. The historical explanation of how defenses developed isn’t all that important in understanding how either operates. To that end, it is best to first examine the basic 3-4 and 4-3 schemes, and then look at the qualities of the secondary.
The 3-4 Defense
The origins of the 3-4 defense go back decades. The base alignment was used in the 40’s and again in the 70’s, but what we really know of as the 3-4 of today started with a unique athlete, Lawrence Taylor, in the 80’s, and coach Dick LeBeau’s use of the zone blitz of the 90’s. Taylor essentially created the role of the outside linebacker as a major pass rush position, and LeBeau perfected the zone blitz, keeping offenses guessing on who is rushing, and who is dropping into coverage.
The 3-4 Defensive Line
The traditional idea of the 3-4 defensive line has three defensive lineman each covering two gaps. Their chief responsibilities are to contain the run and to keep offensive lineman from blocking at the next level. The anchor is usually a huge nose tackle that will command a double team. All three lineman, the nose tackle and defense ends, need to be long armed, have the length to maintain their gap responsibilities, and need to be tall to see over and around offensive lineman.
The 3-4 OLB
One of the core concepts of the 3-4 scheme is that it allows for more players, 4 versus 3, to be in a two point stance. This allows players to react better to quarterbacks in the shotgun. Lawrence Taylor changed the 3-4 outside linebacker position forever in the 80’s; because of him, we now expect this position to be a real threat in pass rush. Today, outside linebackers in a 3-4 are highly sought after players. Because very few colleges play in the 3-4 however, it is a bit tricky for teams to scout. What is generally looked for are smaller defensive ends that have speed coming off the edge, are able to hold up against the run, and are able to drop back effectively in pass coverage. The evaluation process for defensive ends that are considered OLB prospects is extremely tricky as it involves evaluating certain skills that won’t be on a lot of game tape.
The 3-4 ILB
The typical idea of the pair of inside linebackers in a 3-4 is that they work as a complimentary tandem. One is the “thumper” who needs good recognition ability and has excellent strength and tackling skills. He cleans up the gaps for the defense. The other inside linebacker normally has more freedom to freelance. The two are often involved in blitzes together, and work in sync to solidify the middle of the defense, allowing the outside linebackers to make plays.
3-4 Basic Principles
The original, core idea of the 3-4 has 3 defensive lineman taking up as much space as a 4 man front, providing more resources to handle the passing game. Advocates of the 3-4 tout the extra player in a 2 point stance, which theoretically allows for better reactions to what the quarterback is doing. Lawrence Taylor did change the OLB position, putting an emphasis on getting a pass rush from the outside linebacker. As an aside, Taylor did a great amount of that damage essentially lining up in what looks like a 4-3 alignment, however, he didn’t have his hand in the dirt but was upright, so he was technically not a defensive lineman. The 3-4 in its fundamental state didn’t offer a lot with a pass rush, and players like Lawrence Taylor are once in a lifetime. Something else was still needed to make the 3-4 more effective as offenses evolved.
The zone blitz element that flourished under Dick LeBeau added a tremendous element of disguise, confusing offenses. In the zone blitz, popularized in the 90’s at Cincinnati and then at Pittsburgh, under LeBeau, had defenders constantly altering between rushing the passer and dropping into coverage. This was a much needed advancement in the 3-4 as the passing game became more and more prevalent. With the added dimension of the zone blitz, the 3-4 has the pass rushing element needed to be effective against today’s pass happy league.
The 4-3 Defense
The defensive line of the 4-3 is generally set up to have single gap, penetrating lineman. Whereas the 3 defensive lineman in a 3-4 are expected to hold their ground, take up space, and keep runners from getting past them, the ideal 4-3 contains 4 defensive lineman that are moving forward. When working properly, it creates a situation where you have 4 players taking on 5 players (the five offensive lineman).
The 4-3 Defensive Line
Whereas the one nose tackle in a 3-4 really must be a giant with long arms and incredible anchoring ability that takes up a double team, the two defensive tackles in the 4-3 scheme, in theory, don’t need to be as huge, as they are just attacking a single gap and moving up field.
The defensive ends in a 4-3 are the real stars of the scheme. They need to be able to burst off of the snap and get to the quarterback with a variety of pass rush moves, converting speed to power, and making plays.
The 4-3 Linebackers
In a 4-3 the three linebacker positions are given specific names: “Will” for weakside linebacker, or the opposite side of where the tight end traditionally lines up, “Mike” for middle linebacker, and “Sam” for strong side linebacker.
The weakside linebacker does not need to be anywhere near as big as linebackers in a 3-4, but needs to be, in a word, “rangy.” This position will play more free and in more space than the other linebackers.
The “Sam” is most similar to 3-4 linebackers in that he needs to be strong enough to take on blockers and able to cover tight ends.
The “Mike” is really the lynchpin of most 4-3 schemes. The Mike needs to cover a lot of ground and needs to be able to drop into coverage often. Because the two tackles in front of him are most often moving forward and attacking the gaps, the Mike also needs to clean up runners that get through.
4-3 Basic Principles
In a league where passing is key, getting to the quarterback quickly is a premium. The idea behind a 4-3 doesn’t involve as much deception as a 3-4; you simply have 4 players moving forward. This is at its extreme in the NASCAR defense of the Giants a few years back. Now you will often have a NASCAR package with 4 defensive ends lined up on a passing down, getting to the quarterback as quickly as possible.
The key to the 4-3 is that front four. To really make it work you don’t need 4 great players, but more often 6-8. To keep the players fresh, you need to rotate these players, and they need great pass rush skills. You also can’t just have a group of pass rushers, they need to be able to stand up against the run as well. Most often when you see a defense collapse week after week it is a 4-3 without the upfront personnel to run it well. However, if a team can put together a solid front that has depth, finding players to fill out the defense is not too difficult.
Today’s 4-3 and 3-4 Defenses
Most teams will describe their teams as having a “base” of either 3-4 or 4-3, but are often considered “multiple,” meaning they switch up their configuration often. The configuration is not as important as how the defensive front approaches the gaps. Defensive lineman attacking a single gap most of the time are playing into the philosophy of the 4-3, and defensive lineman that are most often anchoring are playing in a 3-4 philosophy. Many 3-4’s look like 4-3’s, but take a quick look for a defensive end playing in a 2 point stance. This is similar to how Lawrence Taylor played, and what you might see in Denver or Houston in 2016.
Moreover, because of the high percentage of pass plays, most teams are playing with an extra defensive back or two almost two thirds of the time. Does this mean that the new base defense in the NFL is the nickel? Not really. Think of it as the Big 10; the concept is still there, but the naming mechanism is off. Yes, most configurations today are probably more often a 4-2 or 3-3, but let’s not quibble.
Corners: Zone and Man
Just as there is nomenclature for differences in defenses (3-4 or 4-3), and offenses (West Coast, Air Coryell, Erhardt-Perkins), the secondary should be viewed as its own entity, with a base “zone” or “man” concept. And as with those other classifications, teams don’t conveniently fit into either a purely zone or man secondary, but all do have a primary concept that they prefer.
In man coverage, a corner will generally face toward the sideline, working the receiver against the sideline. He will have his back essentially to the quarterback with no concern about the run game. Man coverage gives the defender full responsibility for his “man” all the way through his route. He also will “press” the receiver at the line of scrimmage, trying to legally bump the receiver off of his route. Finding a corner that can excel in man coverage is difficult, as they have to turn and run with elite athletes, and when they falter even a little, they get burned for big gains.
In zone coverage, the defender will be aligned differently, much more tilted toward facing the quarterback. They generally are more stout, as they have responsibilities in the run game, and don’t have to follow a receiver all the way down the field. The zone corner is responsible for a receiver up until a certain point and then releases to allow the safety to take over. The corner then moves forward to cover any receivers running shallower routes.
In either man or zone, the traditional defense lineup will have 2 cornerbacks; when added up with 2 safeties, this puts 4 players in the defensive backfield. Nickel (5 defensive backs) and dime (6+ DBs) packages used to be relatively rare, and so a 3rd corner was not considered a starting role. This is changing though, with Nickel packages shown more and more often, the Nickel, or “slot” corner is considered a starting role on some teams. The 5th DB comes at the expense of a linebacker typically, but could also mean the team is short one defensive lineman. If you read our NFL offenses page, you know that in many NFL offenses, anyone, from a tight end to a wide receiver, can run routes in the slot, so the skill set for this new slot receiver needs to be broad. Perhaps the biggest single skill is to be disruptive – get in the way of allowing the play to develop.
The safety position is the position that is probably undergoing the biggest change in both level of importance and utilization. The terms “strong safety” and “free safety” used to clearly define two different roles for safeties, one being used near the line of scrimmage in run support often, and the other having the ability to cover a large part of the field. Today, offenses have been designed to pounce on matchup problems, and safeties were a primary target due to their specific skill sets.
For starters, safeties can no longer be one-dimensional. A safety that is purely a center fielder or a safety that is purely an in the box run supporter would have to be a special team ace that can be used only on specific downs and distances. These guys are becoming more and more rare. Safeties need to be multi-dimensional to a point at least where they won’t be exposed for their weaknesses for that specific down, distance, and field position. Safeties need to be able to be support the run, cover tight ends, blitz the quarterback and play multiple levels of coverage. The more they can do, the more valuable they are.
What defenses are doing now is developing a core of safeties with known strengths and weaknesses that get shuttled in and out of plays. In particular, offenses are using “move” tight ends that can run routes from multiple places along the line of scrimmage that are designed to create mismatches with the secondary. Safeties that can do more help neutralize these mismatches.
At the high-end of the spectrum of safeties is the new super-safety type player. These are safeties that can check skill after skill off the list required for today’s safeties. A few NFL teams have these, and they should be pushing further and further up draft boards.