What is a four-three defense?

What Is a 4–3 Defense in Football?

When you watch an NFL game and see the defense line up just before the snap, you're probably seeing the most common formation in modern football: the 4–3 defense. This setup gets its name from its core structure—four down linemen and three linebackers.

The four down linemen typically consist of two defensive tackles and two defensive ends. Their main job is to rush the quarterback or stop the run right at the line of scrimmage. The three linebackers—usually labeled as the weak-side, middle, and strong-side ‘backers—hang back behind the line, ready to defend the run, cover short passes, or blitz the quarterback when needed.

The 4–3 is considered a base defense, meaning it's the default alignment teams use on first and second downs. It's popular because of its balance. Coaches like it for its flexibility—defensive coordinators can tweak coverages and pressure schemes without having to substitute players or shift into a completely different formation.

Compared to other alignments like the 3–4 (three linemen, four linebackers), the 4–3 puts more pressure on the defensive line to generate a pass rush. That means having strong, athletic defensive tackles and ends is crucial. Teams with dominant front-four pass rushers—think legends like the 1985 Bears or the 2000 Ravens—often built their success around this setup.

While defenses today frequently rotate into nickel (five defensive backs) or dime (six) packages on passing downs, the 4–3 remains the foundation. It's a classic look that blends simplicity with strategic depth, making it a staple in playbooks across the league.