---
slug: "4-3-defense"
title: "4-3 Defense"
depth_tier: formation
side: DEFENSE
category: Fronts
source_id: "DEF-0103"
created: 2026-05-13
updated: 2026-05-13
canonical: https://learningfootball.xyz/formations/4-3-defense
aliases:
  - "4-3 defense"
  - "4-3 alignment"
  - "four-three"
  - "4-3 base"
---
# 4-3 Defense

## Short Definition

Four defensive linemen and three linebackers—one of football's two base defensive alignments, designed to control gaps and stop the run at the point of attack.

## Definition

The 4-3 defense is the base defensive alignment placing four defensive linemen and three linebackers at the second level, with four defensive backs behind them. It is one of the two foundational defensive structures in football—the other being the 3-4—and has been the dominant base defense in the NFL since the 1950s when Tom Landry and others developed it as an answer to increasingly complex offenses.

The four-lineman front gives the 4-3 its gap control foundation. With four defenders at the line of scrimmage, the defense can assign specific gap responsibilities to each lineman, giving the three linebackers cleaner reads and defined run-fit responsibilities behind them. The inside linebacker—the MIKE—is the defense's signal caller, responsible for setting run fits and communicating coverage adjustments. The two outside linebackers align in positions that give them both pass rush access and edge containment assignments.

The 4-3 comes in multiple gap-responsibility variations that define how it plays against the run. In an over front, the defensive line shifts toward the strong side. In an under front, it shifts toward the weak side. These shifts change which gaps the linemen are responsible for and which linebacker must fill versus which has free-runner responsibility. The same 4-3 base can look and function very differently depending on the gap scheme underneath it.

Against the pass, 4-3 teams generate pressure with four-man rushes—the four linemen rush while the three linebackers and four defensive backs drop into coverage. The ability to create pressure without blitzing is a structural advantage of the 4-3: with four dedicated pass rushers on every snap, the coverage defenders can remain in their assignments rather than being committed to pressure.

## Example

"Four linemen on the line of scrimmage, three linebackers behind them—that's your 4-3 base. Four guys whose only job is to get to the quarterback or eat blockers. The whole defense builds from what those four do at the line."

## Common Confusion

The 4-3 refers to the base alignment only—four linemen and three linebackers as a starting point, not a rigid structure for every snap. Modern 4-3 teams constantly use nickel, dime, and other sub-packages. The 4-3 label describes the base, not every defensive snap.

## Related

- 3-4-defense
- 4-2-5
- over-front
- even-front
- bear-front
- nickel-nkl
- mike-re-mike

---
Source: https://learningfootball.xyz/formations/4-3-defense