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The 4-3 Defense
Nomenclature and Alignments
By Richard Linde, 19 April 2002

Are you as confused about the nomenclature and alignments in the 4-3 defense as I am? To get a better understanding of them, I read Bob Kenig’s book, “Football’s Modern 4-3 Defense,” and did some surfing on the Internet. The following is a summary of this task.  

In our definition of the 4-3 defense, four men are positioned on the line of scrimmage in a three-point stance, while three linemen take a three-point stance in a 3-4 defense. That's the simplest definition of the two formations; it becomes  confusing to talk about the ratio of defensive linemen to offensive linemen or other formations, such as an 3-4 Eagle defense. For example, some people will call a 4-3 defense (four linemen in a 3-point stance) an 3-4 Eagle defense because one lineman, in a three-point stance, lines up outside the two offensive tackles (the Rush End Backer) and will drop back into pass coverage.

In the figure below, the letters “A” through “D” represent the gaps between the center and the guards (A gaps), between the guards and the tackles (B gaps), between the tackle and the tight end (C gap), between the tackle and the split end (C gap), and that gap outside the tight end (D gap). The numbers (9, 7, 6, 6i, etc.) represent the possible player alignments, which depend on the offensive scheme. For example, the NT (Josh Miller) could line up in a head-on-the center (0) alignment.

In this figure, a hypothetical 4-3 defense, I’ve penciled in the possible starters for the Huskies during this summer's practices.

The picture above was taken of Greg Carothers (Strong Safety), Picture Day, 2001.

Figure 1. Basic 4-3 Alignments and nomenclature

The nomenclature for the alignments [Kenig] is as follows:

  • 0-head on the center  

  • 1-on either shoulder of the center

  • 2-head on the guard

  • 2i-on the inside shoulder of the guard

  • 3-on the outside shoulder of the guard

  • 4-head on the tackle

  • 4i-on the inside shoulder of the tackle

  • 5-on the outside shoulder of the tackle

  • 6-head on the tight end

  • 7-on the outside shoulder of the tight end

  • 9-outside the tight end

The defensive positions are as follow.

  • NT (Miller) - Stuffs the A gap between the center and guard  (1 or 2i alignment)

  • 3 Technique (DT) (Stevens) - Stuffs the strong side B gap between the guard and tackle (3 alignment). Coaches look for one-gap and two-gap players, ones who can push the pocket back or stay back and cover both gaps between the tackles and guards.

  • DE (Husky, Johnson) – Dawgman.com calls this the Husky. [Samek]. Stuffs the strong side C gap, the one between the strong tackle and tight end (7 alignment). The defensive end forces the play back inside whenever possible.

  • REB (Ellis) - Rush End Backer, attacks the weak tackle one on one (5 alignment). Rushes the QB and contains the run so that it stays between the tackles.

  • SAM – The strong side, outside linebacker is responsible for the TE and making sure that nothing gets outside the DE (5, 6i, 7 alignment). He is responsible for the strong side C gap. Both the WILL and SAM should be able to play either position, lest the offense dictate the defense by moving the TE to the other side of the field, forcing the WILL and SAM to switch positions. [Kenig].

  • MIKE LB – The inside linebacker protects against the run (2i alignment) covering the strong side A gap and the weak side B gap. Although the depth may vary, he usually plays 5 yards off the line of scrimmage. Recognizing the offensive formation, he makes the proper defensive call for the front. He employs a hand shiver to attack blockers and attacks a blocker head on, attempting to go through them [Kenig].

  • WILL LB – The WILL (weak side, outside linebacker) aligns in a 5 alignment when there is an open end and no slot to his side. In that case, he is responsible for the weak side B and D gaps. Otherwise, he is in a 7 alignment when there are two tight ends on the field and is responsible for the weak side D gap. The outside linebackers shuffle parallel to the line of scrimmage until a blocker attacks them. (Kenig).

  • SS - Strong safety. "Run support is primary for a strong safety, but some coverage responsibilities, especially in a zone." [Samek]. In cover 2, the safety is responsible for the deep patterns run by the number 1 and/or number 2 receivers on his side of the field. In cover 2, the SS acts as a free safety, both the SS and free safety being interchangeable. 

  • FS - Free safety. Coverage skills are a must. The free safety is normally the one that covers the deep area unless he cheats up in short yardage or blitz.

  • CB - Corner backs. Covers the split end on the weak side and the flanker on the strong side of the offensive formation. "Washington loves to play man-to-man with their corners but when they play zone the corners will follow their receivers until they leave their box and enter the safety’s zone." [Samek].

Although Kenig's book is well written and liberally annotated with diagrams, the defensive schemes (reads, reactions, and front variations) in his system seem somewhat complicated. It makes me wonder if most 4-3 defensive coaches don’t teach a simpler variation of his method.


Kenig, Bob, "Football's Modern 4-3 Defense," Harding Press, Haworth, New Jersey, 1997.

Samek, David, Editor and Publisher, dawgman.com.

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