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Two Isn't Always Better Than One... But Sometimes... It is.

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The basic premise of this posting is to point out why 2-gap and 1-gap 3-4 defensive systems differ, and how they differ. First off, Iíd be doing a poor job at explaining things if I didnít point out that the Washington Redskins donít use just a 3-4 defensive system. Our scheme is multiple.

When referring to football terminology, multiple refers to the fact that you can run many different fronts/looks. To break it down further, a front is essentially how many defensive players are lined up on the line of scrimmage. So in a traditional 3-4, you have a three front. However, if two of the backers are walked up, you have a five front, but still in the 3-4. The Redskins use the base 3-4 package, they also use some 2-4-5 packages (2 down linemen, 4 linebackers, 5 defensive backs), youíll sometimes see a 1-5-5 alignment, which is often referred to as the ďamoebaĒ defense, and sometimes Youíll see 4-3 looks (although, generally you see one of the ďdefensive endsĒ stood up in a two-point stance rather than with his hands in the dirt. It still falls under the 3-4 package, but itís a 4-3 look).

So letís start off by using some examples of coaches who run the systems. The 1-gap system was originated by Bum Phillips, and was passed on to his son, Wade Phillips. Wade made some tweaks to his fatherís scheme, but in general it remains pretty similar to the original. As far as the 2-gap system goes, itís often referred to as the ďFairbanks-BulloughĒ 3-4 defense. Bill Parcells is one of the guys who used this often, as are Eric Mangini and Bill Belichick.

Now that youíve been provided with examples, letís jump into the meat and potatoes portion of this posting.

The basics of 1-Gap

With the 1-gap system, you over see under front concepts used from time to time. An under concept is something that the Arizona Cardinals use. Basically, the Strong Outside Linebacker (SOLB or SAM) is lined up over the tight end. The Weak Outside Linebacker (WOLB or WILL) is lined up on the other side and is almost always a rusher, although Arizona drops him from time to time. The Nose shifts over to the Strong side A-Gap (Strong is generally the side that the tight end is on) and the End to that side shifts to inside the B-Gap. This is different than the basic 3-4 alignments, which Iíll go over in a bit in detail.

The 1-gap system is an aggressive, attacking defense. You attack your gap first and then make a read. This is a major difference between the 1-gap and 2-gap schemes, the 2-gap is a read then attack defense, which is something else Iíll touch on in a bit.

The 1-gap system is very good for an undersized, quicker defensive line.

Defensive Line Alignments/Gap Responsibilities in 1-Gap
The nose tackle can play a 0-tech (head up on the center) or a 1-tech (shading the shoulder of the center). Sometimes youíll see him aligned in the A-Gap as well. He will have one-gap (hence the term 1-gap) assigned to him. His job is to get to that gap and clog the running lane. Ideally, you want the nose to draw a double team from the guard and the center. This guy has to be a total disruptor. His main role is to free up the inside linebackers to make plays.

The Weak Defensive End (guy aligned away from the TE) has to be a major disruptor as well. You want him to draw the weak side guard over to help the weak side tackle in order to free up the WILL Backer.

The Strong Defensive End needs to take on the tackle and the tight end on run plays.

So, the basic premise is that each defensive lineman needs to attempt to draw a double team each play. There is virtually no glory for these guys. Their job isnít to get sacks, make tackles or dance around on a football field. Their job is to create chances for the linebackers to make plays. They attack a gap and react after attacking in the 1-gap. This is a great defense to use with players who are used to running a 4-3 defense as it doesnít differ in that aspect.

Linebacker Gap Responsibilities/Pass Responsibilities in 1-Gap
The SAM Backer is responsible for the area outside of the tight end versus the run, this is called the D-Gap. Against the pass, heís usually either manned up on the tight end or blitzing. He can play a zone concept.

The Strong Inside Linebacker, often referred to as the MIKE (or various other names, but for the sake of this, Iím using MIKE) blitzed about a quarter to a fifth of the time, but will generally have an underneath coverage versus pass. Against run heíll play the strong side B-Gap.

The Weak Inside Linebacker (or JACK) generally covers the middle of the field (an area often referred to as ďThe HoleĒ). He doesnít blitz as often as the MIKE, blitzing about 1/10th of the time or less. The JACK has 2 run gaps, which is different than the other backers in a 1-gap concept. Generally, heíll play the weak A as the nose will take the strong A, however if the weak defensive end takes an outside rush, the JACK plays the weak B-Gap.

The WILL is the best pass rusher on the team. Against run heíll generally play the weak C-Gap (the area outside the tackle) and he blitzes over 50% of the time. He can and will be used in coverage, but not as often as the other backers.

Now, letís shift focus to the 2-gap.

The basics of 2-Gap
Both offensive guards are generally uncovered. The linebackers cover the ďbubblesĒ (areas) that are over the guards. The 2-gap requires a big, strong, bullish, destructive, dominating defensive line. The defensive line is expected to control both gaps to either side of their alignment (hence the term 2-gap). Similar to the 1-gap, the defensive line is expected to draw a double team, but itís more important here as the guards being uncovered leaves them free to get to a linebacker if the defensive line doesnít do their job. The inside linebackers need to be big enough to take on a guard on every play and must have the ability to shed blocks extremely well just in case the defensive line struggles with occupying more than one blocker. One of the biggest advantages of the 2-gap system is that itís easier to drop eight guys into coverage because the defensive line is each responsible for two gaps. So if the offense runs while youíre dropping eight into coverage, theoretically, it should be taken care of.

One thing is certain, though, the 2-gap is a more difficult system to play. Itís a read then react defense. The guys with plenty of experience in the system, or the guys who possess great football knowledge can play this system very efficiently. They react immediately to the offensive lines movements and diagnose a play. If youíre not used to the 2-gap system, however, it becomes very difficult to diagnose.

Defensive Line Alignments/Gap Responsibilities in 2-Gap
The defensive line will generally play a 5-0-5 technique. Meaning the ends (the 5 portions of the 5-0-5) will both be head up on the offensive tackles. The nose (the 0 portion of the 5-0-5) will be head up on the center.

The Strong Defensive End plays the strong B/C gaps against run and takes on the strong offensive tackle versus pass.

The Weak Defensive End plays the weak B/C gaps against run and takes on the weak offensive tackle versus pass.

The Nose Tackle plays the strong/weak A-Gaps and must ALWAYS draw a double team against run or pass.

Linebacker Gap Responsibilities/Pass Responsibilities in 2-Gap
The outside backers have very similar responsibilities to the ones they had in the 1-gap system. The WILL is the premiere pass rusher on the team and is responsible for the weak C gap versus run. The SAM generally plays the tight end in man coverage, can also drop to a zone and will play the strong C/D gaps.

The Inside backers are slightly different in that they both have 2-gaps to cover. They both play the A/B gaps to their side. The MIKE will blitz more, just like the 1-gap, and the JACK is more of a coverage guy, just like the 1-gap.

Secondary Play in Both Systems
Itís very similar to the 4-3. The main difference is that in a 2-gap system, the strong safety is allowed to roam a bit more. He does a little of everything. In the 1-gap, heís more of a coverage guy traditionally. But these roles have been known to be mixed up in both systems. So those thoughts are more of a generality and often times itís not the case.

Wrap Up
The 2-gap system requires a very specific type of defensive lineman, and larger linebackers than a 1-gap system. Ideally, youíd like to find, big, strong, fast defensive linemen and linebackers for both systems, but itís more important in a 2-gap to have those pieces. The 2-gap requires reading and reacting extremely quickly to be an effective defense. This is why it often takes time for a team making a switch to a 2-gap system to become effective. There is a very steep learning curve.

The 1-gap, when explained, seems a bit more extensive, and in word count it probably is. But there is less diagnosing and more attacking, which makes it quite a bit easier for a team with 4-3 personnel to run.

The 2-gap is the much more popular version of the 3-4 defense, and with good reason. Once itís learned and the proper personnel is in place, itís a very effective attacking defense.

The major advantage that 3-4 defenses have, regardless of 1-gap or 2-gap is the ability to disguise the 4th, 5th, 6th, or even 7th and 8th rusher. Itís multiple and can be used a variety of different ways. The 3-4 system is something that has caught on in the NFL, with merit and good reasoning. But it must be well coached and you must have the personnel to run it, or making a switch is a very difficult and long process.

Updated 12-14-10 at 08:42 PM by Boone



  1. fansince62's Avatar
    very nice there Dawg!

    recommendation: take this defense 101 and apply it to what we have watched all season long with the Skins.....good, bad and the ugly. I know I'd read it closely.

    also....and I'm sure you've thought about this...where do you fall (talent being equal) between 3-4 and 4-3? some of the best defenses in the NFL are still 4-3.


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