D Study

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The defensive team, simply known as the defense, is the team that begins a play from scrimmage without possession of the ball. The objective of the defensive team is to prevent the other team from scoring and win possession of the ball for their side. The defense accomplishes this by forcing the offense to turn the ball over by either preventing them from achieving a first down and forcing them to punt, forcing and recovering an offensive fumble, intercepting a pass, or more rarely, forcing a turnover on downs.

Unlike the offensive team, the rules of the sport do not restrict the defensive team into certain positions. A defensive player may line up anywhere on his side of the line of scrimmage and perform any legal action. Over time, however, defensive roles have become defined into three main sets of players that encompass several individual positions.

Defensive formations are often known by a numerical code indicating the number of players at each position. The two most common formations are the 3–4 defense and the 4–3 defense, where the first number refers to the number of defensive linemen, and the second number refers to the number of linebackers (the number of defensive backs can be inferred, since there must be eleven players on the field). Thus, a 3–4 defense consists of three defensive linemen (usually a nose tackle and two defensive ends), four linebackers, and four defensive backs (two cornerbacks, a strong safety, and a free safety). Some defensive formations will directly indicate the number of defensive backs. The 3–3–5 defense, for instance, has 3 defensive linemen, 3 linebackers, and 5 defensive backs.

Like their offensive counterparts, defensive linemen (also called rushers) line up directly on the line of scrimmage. There are three positions usually considered part of the defensive line:

Defensive tackle (DT)

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Sometimes called a defensive guard, defensive tackles play at the center of the defensive line. Their function is to rush the passer and stop running plays directed at the middle of the line of scrimmage. Most defensive sets have one or two defensive tackles. If one employs a second defensive tackle, sometimes referred to as an under tackle, they are usually a bit faster than the nose tackle.

Nose tackle (NT)

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Sometimes called a middle guard, or nose guard, nose tackles play in the center of the defensive line. Their function is to clog the middle of the offense's line and stop most run plays (more commonly fullback dives, plunges and sneaks). They line up directly in front of the offense's center, almost nose-to-nose, hence the name. This position is used in 3-4 formations, or goal line situations.

Most nose tackles are 320-350 pounds, and are the biggest players on the roster. This position is the most physically demanding, due to being forced into constant double or triple teams, and needing enough speed to collapse the interior of the offensive line. Sometimes, nose tackles are used in 4-3 defenses and are either positioned on the quarterbacks blind side, or directly in front of the center.

Defensive end (DE)

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Defensive ends line up outside of the defensive tackles and are the ends of the defensive line. Their function is to attack the passer or stop offensive runs to the outer edges of the line of scrimmage, which is often referred to as containment. The faster of the two is usually placed on the right side of the defensive line (quarterback's left) because that is a right-handed quarterback's blind side.

Defensive linemen will often take a stance with one or both of their hands on the ground before the ball is snapped. These are known as a three-point stance and four-point stance, respectively, and this helps distinguish a defensive lineman from a linebacker, who begins in a two-point stance (i.e. without a hand touching the ground).

Linebackers (LB)

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This defense (in white) is in a base 4–3 set. Just behind the four defensive linemen (whose hands are on the ground) are three linebackers (numbers 55, 3, and 16), and further back are two safeties (numbers 24 and 44). The two cornerbacks are off screen to the left and right.

Linebackers play behind the defensive line and perform various duties depending on the situation, including rushing the passer, covering receivers, and defending against the run.

Middle linebacker (MLB)

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Sometimes called the inside linebacker, especially in a 3–4 defense, and known colloquially as the Mike linebacker, the middle linebacker is often known as the quarterback of the defense, since they are frequently the primary defensive play callers and must react to a wide variety of situations. Middle linebackers must be capable of stopping running backs who make it past the defensive line, covering pass plays over the middle, and rushing the quarterback on blitz plays.

Outside linebacker (OLB)

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Outside linebackers are given different names depending on their role and the philosophy of the team. Some teams keep their outside linebackers on the same side of the field at all times while others define them as playing on either the strongside (SLB) or the weakside (WLB). The strongside, or Sam, linebacker lines up on the same side as the offensive tight end and often is responsible for covering the tight end or running back on pass plays. The weakside, or Will, linebacker lines up on the side of the offensive line without a tight end and is often used to rush, or blitz, the quarterback or to cover a running back on pass plays. Some are occasionally referred to as edge rushers.

Defensive backs (DB)

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Defensive backs, also known as the secondary, play either behind the linebackers or outside near the sidelines and are primarily used to defend against pass plays. They also act as the last line of defense on running plays and need to be able to make open field tackles, especially when the ball carrier has gotten past the other defenders. A normal defensive lineup includes two cornerbacks and two safeties, though specialty defensive backs (nickelbacks and dime backs) can be brought in in place of linebackers and defensive linemen when there is a need to cover additional receivers.

Cornerback (CB)

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Cornerbacks attempt to prevent successful passes by either swatting the airborne ball away from the receiver or by catching the pass themselves. In rushing situations, their job is to contain the runner, either by directing them back to the middle of the field to be tackled by the middle line backers, or by forcing them out of bounds.

Nickelback / dimeback

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In certain formations, the defense may remove a linebacker or a defensive lineman to bring in extra pass coverage in the form of extra defensive backs. A formation with five defensive backs is often called a nickel formation, and the fifth (extra) defensive back is called a nickelback after the U.S. nickel coin, a five-cent piece. By extension, a formation with a sixth defensive back, known as the dimeback, is called a dime package because it employs a second nickelback and the U.S. 10-cent dime coin is equal to two nickels. Although it is a rare occurrence, a team may also use seven or eight defensive backs on a play.

Safety (S)

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The safeties are the last line of defense (furthest from the line of scrimmage) and usually help the corners with deep-pass coverage. The strong safety (SS) is traditionally the larger and stronger of the two, providing extra protection against run plays by standing closer to the line of scrimmage, usually on the strong (tight end) side of the field. The free safety (FS) is often the smaller and faster of the two, and is typically the deepest player on the defense, providing help on long pass plays