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Fronts (the defensive line)
A defensive front is how many defenders a team puts on or near the line of scrimmage and how they are spaced across it. The front decides who is responsible for which run gap, where the pass rush comes from, and how many defenders are left over to cover.
Read this page before the coverages page. The front sets the math — every defender used to rush is a defender who cannot cover.
Gaps and line alignment
Before the fronts themselves, you need the two pieces of shorthand every front is built from: the gaps between blockers, and the technique numbers that describe where a defender stands.
Gap
The space between two offensive linemen. A run play is designed to hit a specific gap, and every front assigns each gap to a defender. When a defender leaves his gap, that is where big runs come from.
A gap
Either side of the center, between the center and a guard. It is the shortest path to the quarterback and the first gap a short-yardage run attacks.
B gap
Between the guard and the tackle. It is the home of the interior pass rush and of most power runs.
C gap
Between the tackle and the tight end, or outside the tackle when no tight end is attached. It is the edge-setter’s gap.
D gap
Outside the tight end. It only exists when a tight end, wing, or extra lineman is attached to the formation, and it is the gap outside runs and sweeps are aiming for.
Technique numbers
A technique number describes exactly where a defensive lineman lines up relative to the blocker in front of him. Even numbers are head up on a blocker; odd numbers are on a blocker’s outside shoulder. An “i” means the inside shoulder instead. Numbers count outward from the center and mirror on both sides, so a 3-technique exists to the left and to the right.
0-technique
Head up on the center. This is the true nose tackle spot: two-gap, built to occupy the center and often a guard so the linebackers stay clean.
1-technique
On the center’s shoulder, in the A gap. A heavy, space-eating run defender who takes on the center and guard double team.
2i-technique
On the guard’s inside shoulder. It is an A-gap penetrator aimed at beating the guard back into the pocket.
2-technique
Head up on the guard, usually two-gapping and reading the block before choosing a side.
3-technique
On the guard’s outside shoulder, in the B gap. This is the premium interior pass-rush spot — the one-gap penetrator who is asked to create pressure up the middle rather than absorb blockers.
4i-technique
On the tackle’s inside shoulder. Common in 3-4 fronts, where the end squeezes the B gap and lets the outside linebacker set the edge.
4-technique
Head up on the tackle. The classic two-gap defensive end alignment in an odd front.
5-technique
On the tackle’s outside shoulder, in the C gap. The base defensive end spot in a 3-4 front: long, powerful, and responsible for holding the edge against the run.
6-technique
Head up on the tight end. It is a run-first alignment used to keep the tight end from releasing cleanly.
7-technique
On the tight end’s inside shoulder, squeezing the C gap.
9-technique
Outside the tight end’s outside shoulder. It is the widest standard alignment and the speed-rush spot — the alignment a Wide-9 front is named after.
Shade
Any alignment slightly off a blocker rather than directly over him. “Shaded to the weak side” means the lineman has moved off the center toward the side with no tight end.
One-gap vs. two-gap
A one-gap defender attacks a single assigned gap and tries to get into the backfield. A two-gap defender takes on the blocker head up, controls him, and is responsible for the gap on either side. One-gap fronts create more sacks and more big runs; two-gap fronts are steadier and protect the linebackers.
The fronts, most common first
Nickel (4-2-5) — most common in the NFL
Four linemen, two linebackers, and a fifth defensive back in place of the third linebacker. Because offenses spend most of their snaps in three-receiver personnel, this is the real base defense of the modern NFL. It covers the pass better and gives a little back against the run.
4-3 — common in the NFL
Four down linemen and three linebackers. It is the traditional, gap-sound front: each lineman is normally responsible for one gap, and the four rushers are expected to generate pressure without help.
3-4 — common in the NFL
Three down linemen and four linebackers. The linemen usually two-gap and hold blockers so the linebackers stay free, and pressure is harder to predict because any of the four linebackers can rush or drop.
Hybrid / Multiple — common in the NFL
Most staffs no longer live in one base front. They move between odd and even spacing, stand players up, and change personnel snap to snap to keep the offense from setting protection.
Dime (six defensive backs) — situational in the NFL
A sixth defensive back replaces another linebacker, almost always on obvious passing downs. It trades run defense for coverage speed.
Wide-9 — situational in the NFL
A four-man front with the edge rushers aligned in a 9-technique, far outside the tackle, attacking upfield speed-first. It creates sacks, and it opens inside runs, draws, and screens if the rushers overrun the play.
Goal-line 5-2 — rare in the NFL
Five down linemen and two linebackers. The fifth body walks down onto the line, which covers every interior gap and squeezes short-yardage runs. With only two linebackers it is soft against play action and throws over the middle, so it lives in short yardage.
6-1 — rare in the NFL
Six defenders on the line of scrimmage with a single linebacker behind them. It is a goal-line and last-gasp short-yardage look that dares the offense to throw: the run lanes disappear, but one missed tackle becomes a long play.