In American football, each team has 11 players on the field at one time. The specific role that a player takes on the field is called his position. Under the modern rules of American football, teams are allowed unlimited substitutions; that is, teams may change any number of players after any play. This has resulted in the development of three "platoons" of players: the offense (the team with the ball, which is trying to score), the defense (the team trying to prevent the other team from scoring, and to take the ball from them), and the special teams (who play in kicking situations). Within those platoons, various specific positions exist depending on what each player's main job is.
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Offense
In American football, the offense is the side in which the players have possession of the ball. It is their job to advance the ball towards the opponent's end zone to score points. Broadly speaking, the eleven players of the offense are broken into two groups: the five offensive linemen, whose primary job is to block, and the six backs and receivers whose primary job is to advance the ball either running with the ball or passing it. The backs and receivers are also commonly known as skill position players or as eligible receivers (or eligible ball carriers). Offensive linemen are not usually eligible to advance the ball past the line of scrimmage during a play.
The organization of the offense is strictly mandated by the rules; there must be at least seven players on the line of scrimmage and no more than four players (known collectively as "backs") behind it. The only players eligible to handle the ball during a normal play are the backs and the two players on the end of the line (the "ends" or Tight ends). The remaining players (known as "interior linemen") are considered "ineligible", and may only block. Within these strictures, however, creative coaches have developed a wide array of offensive formations to take advantage of different player skills and game situations.
The following positions are standard in nearly every game, though different teams will use different arrangements of them.
Offensive (Interior) line
The offensive line is primarily responsible for blocking. During normal play, offensive linemen do not handle the ball (aside from the snap from center), unless the ball is fumbled by a ball carrier, a pass is deflected and caught by a lineman or when a player who is normally an offensive lineman takes a different position on the field. The offensive line consists of:
Backs and receivers
The six backs and receivers are those that line up outside or behind the offensive line. There are four main positions in this set of players:
Depending on the style of offense the coaches have designed, the game situation, and the relative skill sets of the players, teams may run formations which contain any number of running backs, wide receivers, and tight ends, so long as the mandated "four backs and seven on the line" rule is followed. For many years, the standard set consisted of the quarterback, two running backs (a tailback/halfback and a fullback), two wide receivers (a flanker and a split end) and a tight end. Modern teams show a wide variety of formations, from a "full house" formation with three running backs, two tight ends, and no wide receivers, to "spread" formations featuring four or five wide receivers, sometimes without any running backs. The I formation is one of the most common.
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Defense
The defensive team or defense is the team that begins a play from scrimmage not in possession of the ball. The objective of the defensive team is to prevent the other team from scoring. The defense accomplishes this by forcing the offense to turn the ball over, either by preventing them from achieving a first down and forcing a punt, forcing the offense to fumble or throw an interception, or more rarely, forcing a turnover on downs.
Unlike the offensive team, the rules 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, and several individual positions.
Defensive line
Like their offensive counterparts, defensive linemen (also called rushers) line up directly on the line of scrimmage, close to the ball. There are two positions usually considered part of the defensive line:
Often, though not always, a defensive lineman will have his "hand(s) on the ground," in a three- or four-point stance before the ball is snapped; this distinguishes his pre-snap stance from a linebacker, who begins in a two-point stance (i.e. without a hand touching the ground).
Linebackers
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.
Defensive backs
Defensive backs, also known as the "secondary", play either behind the linebackers or set to the outside, near the sidelines. Defensive backs are primarily used to defend against pass plays. Defensive backs 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 complement of defensive backs includes two cornerbacks and two safeties, though specialty defensive backs (nickelbacks and dimebacks) can be brought in in place of linebackers and defensive linemen, when there is need to cover additional pass receivers.
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 should be eleven players on the field.) Thus, 3-4 defense will consist 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)
Special teams
Special teams are units that are on the field during kicking plays. While many players who appear on offensive or defensive squads also play similar roles on special teams (offensive linemen to block, or defensive players to tackle) there are some specialist roles which are unique to the kicking game.
- Kicker (K)
- Holder (H)
- Long snapper (LS)
- Punter (P)
- Kickoff specialist (KOS)
- Kick returner (KR) and Punt returner (PR)
- Upback
- Gunner
- Jammer
Source of the article : Wikipedia
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