A defense has two jobs at once: stop the run and stop the pass. Every defensive scheme is a balance between the two, adjusted to what the offense does best.
The front: 4-3 and 3-4
- 4-3: four defensive linemen and three linebackers. The line handles most run gaps, freeing linebackers to pursue.
- 3-4: three linemen and four linebackers. Offers more flexibility to disguise which players will rush the quarterback.
Many modern defenses use hybrid fronts and change between them during a game.
Packages against the pass
Because offenses use more receivers than in the past, defenses often replace a linebacker with a defensive back: nickel (five defensive backs) and dime (six). Nickel has become the base defense for many teams.
Coverages
- Man coverage: each defender follows a receiver. Cover 1 adds one deep safety as help.
- Cover 2: two deep safeties split the field; cornerbacks cover the short outside areas.
- Cover 3: three deep defenders each take a third of the field; good against deep passes and solid against the run.
- Cover 4 (quarters): four deep defenders, strong against vertical routes.
Blitzing
A blitz sends extra rushers, usually linebackers or defensive backs, to pressure the quarterback. It can produce sacks and rushed throws but leaves fewer players in coverage. Good defenses disguise blitzes and coverages until the last moment.
Stopping the run
Run defense depends on gap control (each defender responsible for a gap between blockers), setting the edge so runners cannot get outside, pursuit to the ball and sure tackling. A defense that allows big runs often has one player out of position.
Stopping the pass
Pass defense combines pressure and coverage. A strong pass rush shortens the time a quarterback has; tight coverage forces the quarterback to hold the ball. Disguise is key: if the quarterback reads the coverage before the snap, the quarterback knows where to throw.
Countering offenses
Defenses adjust to the opponent: extra defenders near the line against a strong run game, more defensive backs against spread formations, and pressure against inexperienced quarterbacks. Good tackling makes every scheme work; see tackling fundamentals. For the offensive side, read offensive schemes and common plays.
