--- title: "4-3 Defense: Over & Under Fronts, Mike, Will, Sam" description: "The 4-3 defense puts four linemen up front with three linebackers behind. Learn over and under fronts, Mike, Will and Sam roles and one-gap run fits." url: "https://www.coachboard.app/library/american-football/4-3-defense" sport: "American Football" category: "Tactic" level: "intermediate" dateModified: "2026-09-24" --- # 4-3 Defense — American Football Tactic The 4-3 defense is an American football front with four down linemen and three linebackers (Sam, Mike and Will), where each player usually attacks one gap to stop the run. The 4-3 is built on a simple idea: put four linemen on the ball, give each of them one gap to attack, and let three linebackers fill what is left. Because more gaps are controlled right at the line of scrimmage, linebackers can play fast and downhill instead of waiting for blockers to be absorbed. It is one of the most widely taught base defenses from high school to the NFL. What separates a good 4-3 from a basic one is the front call. By shifting the line toward or away from the tight end, the defense changes which linebacker is protected, where the 3-technique rusher sits and who has to take on the fullback. Over and under fronts are the two calls every 4-3 coach installs first. ## Objective Stop the run with one-gap linemen and fast linebackers, and generate a four-man pass rush without blitzing. ## Setup - **Area:** Tackle box to the edges, line of scrimmage to about 7 yards deep - **Players:** 7 front defenders (4 linemen, 3 linebackers) against a scout offense with a tight end - **Equipment:** 1 ball, Stand-up bags for scout linemen, Cones to mark each gap - **Duration:** 15–20 minutes of front install per practice for the first two weeks - **Level:** intermediate (U12+) ## How it works 1. **Identify the strength** — The Mike calls the offensive strength before the snap, usually the tight end side or the side with more receivers. Every front call and linebacker alignment keys off that call, so it has to be loud and early. 2. **Set the Over front** — In an Over front the line shifts toward the strength: the strong-side tackle sits in a 3-technique on the outside shoulder of the guard, the nose shades the center to the weak side, and both ends align in 5-techniques outside the tackles. The Sam stacks or walks up over the tight end, the Mike aligns off the ball in the middle and the Will plays off the weak tackle. 3. **Set the Under front** — In an Under front the line shifts away from the strength: the 3-technique moves to the weak side, the nose shades the center to the strong side, and the Sam walks up on the line over the tight end as a stand-up edge player. The weak-side end plays wide to rush. Under protects the Mike and Will from guards climbing to the second level. 4. **Fit the run by gap** — A tight end gives the offense seven gaps along the line, and a lead back adds an eighth. Four linemen take four, the three linebackers take three more, and a safety rolls down to the last one. Draw every gap letter on the board and give each defender one. 5. **Rush four, drop seven** — On passing downs the four linemen rush, with the 3-technique and weak-side end as the main threats. The three linebackers drop to hook and curl zones or pick up backs and tight ends in man coverage, matching whatever coverage the secondary plays behind them. ## Coaching points - Linemen attack their gap with the near foot and near hand, then find the ball; a one-gap player who reads first gets washed out. - The Mike reads the guards: a guard stepping at him means run, a guard setting back means pass. - The Will is the linebacker most often kept clean, so he should be the fastest pursuer and the most reliable open-field tackler. - The Sam takes on the tight end and fullback with his inside arm free, spilling or squeezing the run according to the call. ## Variations - **4-3 with a nickel** — Replace the Sam with a nickel defensive back against three-receiver sets. The front stays four down, but the defense gains a coverage player on the slot, which is how many modern teams play most snaps. - **Wide 9 ends** — Align both ends far outside the tight end or tackle to rush on long-yardage downs. It creates speed around the edge but opens bigger interior gaps, so linebackers must fill quickly against the run. ## Build it in Coach Board Build the Over front on a Coach Board field with gap letters next to each defender, then duplicate that board and slide the line to make the Under front, so your linebackers can flip between the two and see exactly who moved. Animate a power run against each board and share both as links before practice so the Mike can rehearse his strength call at home. [American Football coaching app](https://www.coachboard.app/sports/american-football) · [Start 14-day free trial, no card](https://my.coachboard.app) ## FAQ ### What do Mike, Will and Sam mean in a 4-3 defense? They are the three linebacker names. The Mike is the middle linebacker who makes calls and fills inside. The Will is the weak-side linebacker, usually the fastest and often left unblocked. The Sam is the strong-side linebacker who plays over the tight end and takes on blocks at the point of attack. ### Why is the 4-3 good against the run? With four linemen attacking gaps at the line of scrimmage, the offensive line has fewer free blockers to climb to the linebackers. That keeps the three linebackers clean, so they can read the play and fill quickly. Adding a safety in the box gives a defender for every gap. ## Related - https://www.coachboard.app/library/american-football/3-4-defense.md - https://www.coachboard.app/library/american-football/linebacker-drill.md - https://www.coachboard.app/library/american-football/cover-2-defense.md - https://www.coachboard.app/library/american-football/inside-zone.md --- [American Football coaching app](https://www.coachboard.app/sports/american-football) · Animate and share this tactic with your team: https://my.coachboard.app