ITP Glossary: 3-4 Base Defense

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3-4 Base Defense

The 3-4 base defense consists of three defensive lineman (a nose tackle and two defensive ends) and four linebackers (two inside linebackers and two outside linebackers) and features a one or two gap responsibility for the defensive lineman, depending on the scheme. Traditionally, this differed from the 4-3 defense, as the defensive linemen in a 3-4 front are primarily concerned with occupying the offensive linemen in order clog running lanes and allow the linebackers to flow to the ball, or pressure the quarterback.

Although used in college football at the University of Oklahoma since the 1940s, the 3-4 defense became a staple in the 1970s and 1980s NFL before offenses adjusted and attacked its weaknesses, reducing its usage to just a handful of NFL teams by the 1990s and early 2000s. The benefit of this defensive front is that it allows the defense to put 4 to 5 players at the line of scrimmage to stop the run, allowing for a variety of players to become the 4th ‘rusher’, while also dropping 1 to 2 players into coverage to confuse the offense. The 4th and / or 5th rusher then can blitz through any gap as well, creating confusion and personnel mismatches for the offensive line. The 3-4 front creates a large variety of different looks for the offense to combat, with the QB and OL not always knowing where the blitz will come from. As a result, this defense simultaneously stuffed the run from the powerful new running backs of the 1970s and 1980s while also allowing the defense to drop eight players into coverage to prevent big pass plays.

There are two different gap responsibility systems to be concerned with when discussing the 3-4 defense: One-gap versus two-gap responsibility for the defensive linemen. In a two-gap system, the three DL are responsible for controlling both of their assigned gaps (the NT both A gaps, the DTs the B and C gaps) by reading the play and flowing to the appropriate gap. The linebackers then flow into the gaps not filled by DL to provide full gap coverage and prevent cutback lanes in the run game, allowing the defense to blitz through those gaps. Additionally, in a 2-gap system, the ILBs may flow freely to the ball without filling an assigned gap. The result is a versatile system that adapts based on the offense’s play call. In the one-gap system, each of the front seven players are responsible for defending a single gap. By removing the mandatory read and react component of a DL’s responsibility in a 2-gap system, defensive line’s can be quicker and more decisive attacking an offense, but forcing the inside linebackers to be disciplined to a gap.

Traditional 2-Gap 3-4 or “Okie” Front

In a traditional or “Okie” front 3-4 system, the defensive line lines up a nose tackle as a 0 technique and two 5 technique defensive ends who have 2-gap responsibilities in the run game, meaning the DL will read the play and react or flow to fill the appropriate gap. Read and react is mandatory in the 2-gap system. The defense in this front has many options with their linebackers in terms of their pre-snap placement. The strongside, or Sam, linebacker can play on the line in a 2-point stance to assist in run support as a 6 or 7 technique. Opposite him, the weakside, or Will, linebacker can play on or off the line to assist with contain in the event of a run, or play the flat zone, or trail the RB, in a passing situation. The two inside linebackers (Mike and Jack backers) can be responsible for covering the gap the defensive end and nose tackle did not cover in a run situation, but are allowed to flow to the football without allegiance to a particular gap. In passing situations, these ILB may blitz or drop into coverage to protect the hook / curl zone and protect against crossing routes.

The defense will usually rush one of these linebackers as a fourth rusher. The blitzes can come from the interior from either the Jack or Mike, or from the Will or Sam looping into the the A or B gaps, or from the edge, by sending the Sam or Will linebackers. This front also allows the defense to attempt an overload blitz scheme by sending both Jack and Will LBs on blitzes behind the DE, giving the defense a 3 on 2 matchup.

Below, the 2014 Philadelphia Eagles defense, lead by coordinator Bill Davis, lines up in a 3-4 Okie front against the San Francisco 49ers. The three down lineman, Cedric Thornton, Bennie Logan, and Fletcher Cox are lined up in a 5 tech-0 tech-5 tech formation and all have two gap responsibility. OLB Connor Barwin is responsible for the weak side and protects the flat on this play. The strongside OLB, Trent Cole, has contain responsibility, while the two ILB, DeMeco Ryans and Casey Matthews, are free to flow to the ball and not an assigned gap:

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1-Gap 3-4

Oail Andrew “Bum” Phillips, father of current Denver Broncos defensive coordinator Wade Phillips, is widely accepted as the creator of the 1-gap 3-4 defense as a response to not having enough linemen to produce a quality starting four man front. Phillips focused his front to attack the passing game, instead of stuff the running game. He did this by implementing 1-Gap responsibilities for the linemen, meaning rushers can attack their assigned gap quickly and efficiently while the linebackers can also confuse the OL and the QB by mixing up which gaps they are blitzing through.

Traditionally in this front, the nose tackle still plays a 0-technique while the two defensive ends shade in a bit to play a 4i-technique (across inside shoulder of the offensive tackle). Working on the inside shoulder of the offensive tackle helps the DE tie up guards so they cannot reach the second level as quickly and neutralize the inside linebackers. The Sam has the option to play over the TE in a 6 technique and is responsible for playing a 2-gap role (“Eagle” front). The Will is responsible for the cutback lanes on runs and the flats on a potential bootleg. This traditional front is not commonly used in the modern game, and defensive coordinators have made small adjustments to disguise it. Sometimes the DEs will line up directly across from the OT, or the NT will not play a true 0 tech and angle his body in either direction. But the key to identifying this front is to watch what the down linemen do post snap, if the two DEs engage the inside shoulder of the OTs and the NT attacks the A-gap, then it is considered the 4 tech-0 tech-4 tech base 3-4 defense.

Each down lineman is responsible for a single gap, with that gap varying by defensive play call. The fourth rusher will vary and can utilize open gaps along the line to slip through at attack the passer. A 1-gap system is built more with attacking the passer and disrupting the backfield in mind, when compared with the 2-gap variety. Gregg Williams, Jim Schwartz, and Jim Washburn utilize an “attack and react” method where defensive linemen set in an attack stance, key the ball or snap count, and look to penetrate the offensive line. If the OL employs a reach block, or the DL misses his gap, the ILBs convert to 2-gap players and fill the missed gap. The idea behind the method is that disrupting the play at the mesh point is more beneficial to stopping the offense than filling the assigned gap.

On the following play from 2015, the Denver Broncos show a 3-4, 1-gap front. Derek Wolfe (#95) lines up across from the LT, while NT Sylvester Williams is slightly offset from the center but still in a 0 technique. Malik Jackson (#97) is lined up to the inside shoulder of the RT. Both OLBs, Von Miller (#58) and DeMarcus Ware (#94), are walked up on the line in two point stances. Strong side ILB Brandon Marshall (#54) is sugaring the B Gap, while weakside ILB Danny Trevathan is playing in a natural position. After the ball is snapped, both DEs attack the inside shoulder of the OTs, signifying a 4 technique.

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Philip Kibbey wrote this entry. Follow Philip on Twitter @ITPPhilip. Dan Hatman contributed to this entry. Follow Dan on Twitter @Dan_Hatman.

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