There are 11 players on Offense and 11 players on Defense.

The Defense are the 11 players on the field that are trying to stop the opposition moving the ball up the field to score in the end-zone. The various positions have many different responsibilities and require different attributes in the players.

A typical 4-3 defensive formation may look like the below diagram.

The positions are as follows:

Cornerback (CB)
These guys are primarily responsible for taking of the offense's wide receivers. Therefore they have to be quick and it is useful if they can catch (or at least jump) like a wide receiver as intercepting or deflecting the ball is desirable. There are usually 2 of these guys in the defense.

Safeties - Strong Safety (SS) & Free Safety (SS)
Safeties are the last "line of defense" as they are often found much further back in the defensive formation (10 yards away from the line-of-scrimmage is not uncommon). Being so far back away from the play, they must be fast to get to where the action is, or cover a wide receiver coming into their area (or "zone"). The strong safety lines up on the same side as the offense's Tight-End, the Free Safety is on the opposite side. It's useful if Safeties are big as well as quick as they sometimes have to tackle big running backs that have broken through the linemen and linebackers. There is usually 1 strong safety and 1 free safety in the defense.

Linebacker (LB)
The linebackers have probably the toughest job in the defense as they have a wide range of responsibilities, and are usually the captains of the defense, They line up behind the defensive line (hence the name linebacker). They are versatile as they must be fast enough to chase running backs and intelligent enough to defend passes to wide receivers or tight-ends. The linebackers must be courageous enough to plug holes in the defensive line, to stop running backs. In a typical 4-3 defense, there are 4 linemen and 3 linebackers, in a 3-4 defense, there are 3 linemen and 4 linebackers.

Defensive End (DE)
The Ends are primarily there to put pressure on the Quarterback. This forces him to throw before he's ready and hopefully miss his receiver. Ends are usually tall, strong and fast as they have to get by the offensive tackles, who are usually big guys, to get to the QB. The Ends often have 'contain responsibility' which means that nobody should run around the end of the defensive line with the ball.

Defensive Tackle (DT)
The tackles are usually big guys as they often have to try and stop running backs coming straight through the middle of the defensive line. They are also trying to power their way through the offensive line to get to the QB. In a typical 4-3 defense, there are 2 defensive tackles.




The offense is the part of a team which focus is on scoring points to win the football game.

Offensive Positions:
Quarterback(QB)--In most cases, the quarterback is the leader of a football team. A quarterbacks is like the platoon Sargent who follows and adds to the tactics used in each play. This occurs when the QB recognizes that the defense's play will render the offense's planned play ineffective. He would then call an "audible" to quickly revert to another play. The play begins when the QB shouts the proper "cadence" or "snap counts" signaling the ball to be "snapped"--i.e. a quick hand-off to the quarterback. Most of the time, balls are passed by this player so he must be a skillful thrower. As a well-rounded player, the quarterback must also be fast enough to avoid incoming defenders(called "rushers" in general) whose sole purpose is to take him down. If he does make contact with the defense, he must be strong enough to resist being tackled or merely be able to handle a tackle. In addition, the QB must be able to make quick decisions because of the variability that can exist in each play. In plays that do not have the QB passing the ball, the quarterback himself is not allowed to receive any "forward passes"--passes that result in the ball advancing towards the endzone.

Running Backs(RB)(FB)--Also known as the "backs", these positions can be separated into both "halfback"(HB) and "fullback"(FB) The two "backs" share similar responsibilities of starting each play close to the quarterback and either block incoming rushers or they have the ball "handed-off" to them in which they will typically run with it. Halfbacks usually tries to avoid contact with the defense in running plays but fullbacks, with their bigger physiques, will try to run through a pack of linemen to score that extra yardage for a first-down or a touchdown.

Wide Receiver(WR)--Obviously, their primary job is to run far away in a certain pattern to elude their defenders and then catch a passed ball. Usually, receivers are fast and quick--they can change their direction with great ease to throw off their defenders--as well as being able to demonstrate great finesse to receive balls that are positioned in a way that makes it hard for them to catch.

Offensive Linemen(OT)(G)--Linemen are the ones who are lined up against the defense and are closest to the ball before play starts. They represent the 'defense of the offense'--their job is to block the rushers from coming in and knocking out the quarterback. Moreover, they can push the defense away a particular area to create a "hole" in which the ball carrier can slip through and run forward. Like the quarterback, OL are not permitted to catch forward passes too.

Tight End(TE)--The player in this position are a hybrid of linemen and wide receivers. He is positioned between the the two and they block and receive on certain plays. Given the nature of the job, the TE must obviously be bigger than wide receivers but they have to be able to catch a ball when the time comes. Since there is only one TE, he can be positioned on either sides of the linemen; the side he is on is called the "strong side" and the other side is called the "weak side."




Sources used for this information:
www.football.com
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