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Explaining the 3-4 defense

The 3-4 defense is a complicated one, so we'll explain some of the positions for you.


The Jacksonville Jaguars defensive scheme going forward has yet to be determined, as new general manager David Caldwell told reporters in his introductory press conference he would let the coaching staff decide on defensive scheme. This leaves open the possibility for the Jaguars to make the transition to a 3-4 defense.

This leads to a lot people wondering what all that entails and what the team would need to do going forward, including which players on the current roster would fit in.

Let's review the responsibilities and basics of a 3-4 defense.

The biggest difference in a 3-4 defense is on the defensive line, which as the number signifies, utilizes only three down lineman. It usually consists of a nose tackle and two defensive lineman. These players however generally have specific responsibilities and are often described by the technique in which they play.

Such as a 3-technique, 5-technique, 0-technique, and so on. The method at which these positions are defined are by a numbering technique developed by Bear Bryant.


As you can see, the numbering system starts with the 0-technique, which lines up directly over the nose of the center on the offensive line. From there, the system expands all the way to the 5-technique which plays the outside shoulder of the offensive tackle.

Each odd number on the numbering system plays a shoulder of the corresponding offensive lineman whereas the even numbers play over the offensive lineman, directly. On a standard 3-4 defensive line, you're going to have a 0-technique at the nose and two 5-technique defensive ends.

This will generally require the defensive ends to play two gaps on defense, generally playing the C-gap (outside the tackle) and the B-gap (between the guard and tackle). This also means that the 0-technique nose tackle will play the A-gap (between the guard and the center), but really will be playing two gaps because there is an A-gap on either side of where they line up.

Got it?

Now, there are variations of the 3-4 defense, such as what the Houston Texans run under Wade Phillips, which while it is a 3-4 defense, it's really a 5-2 defense. Phillips defense utilizes a lot of 1-gapping from his defensive line and two outside linebackers. The roles of his defenders are usually a bit different than the "true" 3-4. Typically the strong side linebacker (SAM) will line up as a 9-technique while the right defensive end will line up as a 5-technique. The nose tackle will generally play a 1-technique with the left defensive end playing the 3-technique and the weak side linebacker (the designated rush backer, or commonly in a 3-4 the JACK) will play the 5- or 7-technique depending on the situation.

Got all that?

As far as who on the Jaguars could play these various positions, I think you can look at it like this (not including players who's contracts are expiring):


Tyson Alualu
Austen Lane
Jeremy Mincey


Tyson Alualu
Austen Lane
D'Anthony Smith
C.J. Mosely

0 or 1-technique:

C.J. Mosely
Jeris Pendleton

JACK linebacker:

Jeremy Mincey
Andre Branch
Jason Babin
Austen Lane (though, I could be very alone in this notion)

So, now when Mike Mayock says a draft prospect is "best fit as a 5-technique" or that an outside linebacker is a "JACK" or a "SAM" you'll know what he's talking about.