Editing Linebacker (section)

==Formations==
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The number of linebackers is dependent upon the [[Formation (American football)#List of Defensive formations|formation]] called for in the play; formations can call for as few as none, or as many as seven. Most defensive schemes call for three or four, which are generally named for the number of linemen, followed by the number of linebackers (with the [[46 defense]] being an exception). For example, the [[4–3 defense]] has four defensive linemen and three linebackers; conversely, the [[3–4 defense]] has three linemen and four linebackers.

===4–3 defense===
{{Main|4–3 defense}}
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In the 4–3 defense there are four down linemen and three linebackers. On pass plays, the linebackers' responsibilities vary based upon whether a man or zone coverage is called. In zone coverage, the linebackers will generally drop into {{clarify|text=hook zones|date=November 2022}} across the middle of the field. However, some zones will send the outside linebackers into the flats (area directly to the left and right of the hash marks, extending 4–5 yards downfield). In a man-to-man call, the "Sam" will often cover the tight end with help from a safety over the top, while at other times, the "Sam" and "Will" will be responsible for the first man out of the backfield on their side of the center, with the "Mike" covering if a second man exits on that side of the field.

In the "[[Tampa 2]]" zone defense, the middle linebacker is required to drop quickly into a deep middle zone pass coverage thus requiring a quick player at this position.

===3–4 defense===
{{Main|3–4 defense}}
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[[File:Linebacker34.svg|thumb|A base [[3–4 defense]]]]
In the 3–4 defense three linemen play the line of scrimmage and four linebackers back them up, typically two outside linebackers and two inside linebackers. 

The idea behind the 3–4 defense is to disguise where the fourth rusher will come from. Instead of the standard four down-linemen in the 4–3, only three players are clearly attacking nearly every play. The focus of the 3–4 defensive line is to occupy offensive linemen thus freeing the linebackers to tackle the running back or to rush the passer or otherwise drop into pass coverage.

The outside linebackers in a 3–4 defense line in front of the tackles like true defensive ends. The outside linebackers in a 3–4 defense must be very skilled at rushing the quarterback, and would be playing defensive end in a 4–3 defense. Among inside linebackers, one is generally a run-stuffer who is better able to handle offensive linemen and stop running backs, while the other is often a smaller, faster player who excels in pass coverage. However, the smaller or cover LB should also be able to scrape and plug running lanes decently.

The design concept of the 3–4 defense is to confuse the offensive line in their blocking assignments, particularly in pass blocking, and to create a more complex read for the quarterback. Many 3–4 defenses have the ability to quickly morph into a 4–3 on the field.

===46 defense===
{{main|46 defense}}
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In the 46 defense, there are four linemen, three linebackers and a safety who is moved up behind the line of scrimmage. Thus, it appears as if there are four linebackers, but it is really three linebackers with one safety playing up with the other linebackers.

Three of the defensive linemen are over both of the offensive guards and the center, thereby making it difficult to double-team any one of the three interior defensive linemen. This can also take away the ability of the offense to pull the guards on a running play, because this would leave one of the defenders unblocked, or, at best, give another lineman a very difficult block to make on one of the defenders. The safety, like the linebacker, can blitz, play man-on-man, play zone, or drop back into deep coverage like a normal safety would do. The 46 is used in heavy run situations to stop the run, when a team wants to apply much pressure, or merely to confuse the [[quarterback]] and offensive line.

===4–4 defense===
{{Main|4-4 defense}}
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This defense is effective at run-stopping but is weaker than a 4–3 defense at pass coverage because it uses only three defensive backs. This defensive scheme is often played with two inside line backers and two outside line backers. The names of the two inside line backers are often called Sam and Mike and these two are lined up about four yards from the line of scrimmage and are lined up with the offensive guard. The inside line backers are often more of a run player so they will defend the run before they will the pass. These line backers will be reading the offensive guard so they know what to do, so if the guard sets up to pass block the line backers know to get into their zone in order to cover the pass. If the guard come out for a run play they know that they need to fill the gap that they are supposed to so that they can make a play if it comes to them. Also, these inside line backers are often called on a blitz which is when no matter what the offense does, as soon as that ball is snapped they are shooting their gap and trying to get into the back field to make a play as fast as possible. Outside line backers sometimes are considered to be pass players before they are run players. But that depends on where they are lined up, if they are outside of the box of the defense then they will be pass first players, but if they play inside the box lined up behind the defensive end then they are typically a run player. One of the outside linebackers is usually called into either blitz or pass coverage to make up for the missing defensive back. In the NFL and college football, this alignment is used mainly in short yardage situations or near the goal line. It is commonly used in high school football.