The Different Looks of the 4-3 Defense

The 4-3 defense is a common defense among professional and even youth programs. It’s easy to install and allows for teams to use different personnel at different positions.

The 4-3 defense requires 4 defensive lineman and 3 linebackers. The 3 linebackers are often called the Sam, Mike and Will linebackers.

In this article, we’re going to learn more about the 4-3 defense and the different varieties of defensive sets.

The 4-3 Defense

While defenses in the NFL run a variety of schemes, the 4-3 defense is a staple in essentially every playbook. A 4-3 defensive look, by nature, consists of 4 defensive lineman and 3 linebackers. Within this 4-3 personnel grouping, there are multiple different looks a defense can use to stop an offense.

Regardless of the alignment, the 4-3 defensive front, this scheme is all about gap control. Each player has the responsibility of one gap. With that in mind, let’s look at a few different alignments we are likely to come across in a game.

4-3 Base

The base 4-3 look has no shading or shifting of personnel to one side of the field. The interior DT are lined up over the Guards, the DE’s are outside of the Tackles with Outside backers lined up over the Tackles and the Mike backer lined up on the Center.

As the game evolved, we saw how the 4-3 was altered to provide different looks.

4-3 Over

As depicted above, the “Over” alignment calls for a slightly different look than the base call. We have a DT lined up in the “Open” or Weak-Side A-gap, with the other DT lined up in the B gap of the opposite side.

The DE on the “Closed” or Strong-Side is head up on the Tight End while the Open side DE is split wide. The Linebacker corp is noted above as being lined up to have gap assignments that fit perfectly with what the defensive line could not match up with.

Lastly, note that “Tan-Zero-Tan” as written above the linebackers refers to Tan meaning to shade the Tackles and Zero to being over the Center.

4-3 Under

The “Under” alignment is most notably different in the way the linebackers are dispersed. The ‘Sam’ backer is left most backer in the picture above with responsibilities of the D gap, the ‘Mike’ backer is now on the Closed side B-Gap, and the ‘Will’ Backer is on the Open-side A gap.

The defensive ends both have C-Gap responsibilities while Strong-Side DT is in the A-gap and the Weak-Side DT is in the B gap.

Overview Of 4-3 Linebackers

The “Sam” linebacker, is normally lined up on the across from the tight end. There is a fair share of blitzing that can be done from this position, but this backer is big in stopping the run. Because of this, they are usually a bigger linebacker  than the “Will” backer.

Finally, he will usually be relied upon to cover the tight end or potentially a back out of the backfield.

The “Will” linebacker, will generally play on the weak side and typically has more freedom than the other LBs. Of the 3 backers, the Will is most likely to be blitzing and is normally responsible for guarding against the screen. Generally, they also have  heavier coverage responsibilities.

There is a good number of Will linebackers in the NFL that are former safeties because of this.

The “Mike” linebacker, if of course the linebacker in the middle. He has to be a downhill force stuffing the run up the middle while being versatile enough to also drop into coverage for zone or man schemes.

Coverages Used In The 4-3 Defense

Due to the fact that most of the resources are dedicated to the run, there’s a limited amount of coverages that a 4-3 defense can run. Having 7 defenders in the “box”, trying to stop the run, that means we’ll have 4 pass defenders playing coverage.

Man Coverage

First, and most simple, is man coverage. Teams are able to play man coverage by matching up the 4 defensive backs with the 4 receivers. Teams will typically have one of the 3 linebackers play man coverage on the running back out of the back field.

This defensive coverage is most effective if the defensive back’s skill are greater than that of the wide receivers. If the wide receivers are talented, this may cause an issue for the defensive backs, as they have no deep help.

Cover 2

Cover 2 is a common coverage played out of a 4-3 defense. It allows for the 3 linebackers to still be dedicated to the run, but still cover enough ground for the pass. The three areas that will be covered are the hook/curl areas and the middle of the field.

The weakness, being the middle of the field in a cover 2, relies on the middle linebacker to drop into coverage to intercept any crossing routes. As the cover 2 isn’t a perfect deep coverage, it does enough to disrupt any low crossing routes.

Why Run The 4-3 Defense?

Offenses have the ability to run anything from the spread offense to a power run (I-formation) attack.

Having a base defense that is versatile enough to produce different looks is crucially important for a defense. The 4-3 Under is almost a 5-2 front that puts the defense in a position to dominate the line of scrimmage.

The 4-3 is most effective when the 4 defensive lineman can not only protect their gap against the run, but get after the passer.

This defense is designed to stop the run with the gap assignments but can be exposed when there is no pressure on a passing attack. At high levels of football, the 4-3 is just a piece of what a defense does and should be mixed in with other looks.


The 4-3 defense is often played against 21 personnel or 22 personnel offenses. To learn more about why personnel matters in football and how to play to your advantage, check out this blog here.

4-3 defenses are often played by coaches who face power offenses. Now that offenses have moved to a more traditional spread look, defenses are forced to match speed with speed. This often requires taking a linebacker off of the field and running and 4-2-5 defense rather than a 4-3.

Do you run a 4-3 defense? Do you have questions about the 4-3 defense? Let us know in the comment section below how you run the 4-3 and what’s been the most effective for you.

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