Quarterback

Quarterback (QB, originally called blocking back) is a position in American and Canadian football. Quarterbacks are members of the offensive team and line up directly behind the offensive line. Quarterbacks are the leaders of the offensive team, responsible for calling the play in the huddle.

Every play starts with a "snap", an action where the offense's center gives the ball to the quarterback, or as a trick play to another offensive player such as a wide receiver. After receiving the ball, the quarterback either throws a pass or hands it to another offensive player; in some cases, the quarterback keeps the ball in an attempt to run or "scramble" past the defense.

At most levels, but especially at the college and professional level, the quarterback role is one of the most visible and important roles on the team. The quarterback touches the ball on nearly every offensive play and has a great deal of responsibility both in calling plays and making decisions during the play. While there is liberal substitution at most positions in football based on the play call and to minimize player fatigue, most quarterbacks are on the field for every offensive play leaving only for injury or when the game's outcome is no longer in doubt. Quarterbacks are frequently chosen early in the NFL Draft and often receive much more lucrative contracts than other positions. As of 2010, players in this position have won more Super Bowl MVP awards (23 of 44) than players at all other positions combined.

As the term "quarterback" gained acceptance in the 1930s, it originally referred to the player's position relative to other members of the offensive backfield. Before the emergence of the T-formation in the 1940s, all members of the offensive backfield were legitimate threats to run or pass the ball, and most teams used four offensive backs on every play: a quarterback, two halfbacks, and a fullback. The quarterback began each play a quarter of the way back, the halfbacks began each play side by side and halfway back, and the fullback began each play the farthest back. Now that most offensive formations have only one or two running backs, the original designations do not mean as much, as the fullback is now usually a lead blocker (technically a halfback), while the halfback or tailback (called such because he stands at the "tail" of the I) lines up behind the fullback.

Traditionally, quarterbacks have been responsible for calling the team's offensive plays based on the defense's formation, or game situation. To choose the proper play, quarterbacks often spend time rehearsing and studying prearranged plays during their team's practice sessions.

In recent years, the rise of offensive coordinators has led partiality toward a scripted game plan. The offensive coordinators and coaches usually give the quarterback information via a built-in headphone in the helmet as to what to do before the play. Quarterbacks are allowed to hear, but not talk to, their coaches until there are fifteen seconds left on the play clock. The quarterback then relays the information to teammates and executes the plays. When the players are set in a formation, the quarterback starts the play by calling out a code word, a number, or a combination of the two.

Dallas Cowboys head coach Tom Landry was an early advocate of taking play calling out of the quarterback's hands. Although this remained a common practice in the NFL through the 1970s, fewer QBs were doing it by the 1980s and even Hall-of-Famers like Joe Montana did not call their own plays. Buffalo Bills QB Jim Kelly was one of the last to regularly call plays. Among current NFL QBs, Peyton Manning of the Indianapolis Colts and Matt Ryan of the Atlanta Falcons call all, or nearly all, of their team's plays using a no-huddle offense, although they mostly just make adjustments to the plays given to him from the offensive coordinator.

Special tactics
If quarterbacks are uncomfortable with the formation the defense is using, they may call an audible change to their play. For example, if a quarterback receives the call to execute a running play, but he notices that the defense is ready to blitz – that is, to send additional defensive backs across the line of scrimmage in an attempt to tackle the quarterback or thwart his ability to pass – the quarterback may want to change the play. To do this, the quarterback yells a special code, like "Blue 42," or "Texas 29," which tells the offense to switch to a specific play or formation.

Also, quarterbacks can "spike" or throw the football at the ground to stop the official game clock. For example, if a team is down by a field goal with only seconds remaining, a quarterback may spike the ball to prevent the game clock from running out. This usually allows the field goal unit to come onto the field, or attempt a final "Hail Mary pass". However, if a team is winning, a quarterback can keep the clock running by kneeling after the snap. This is normally done when the opposing team has no timeouts and there is little time left in the game, as it allows a team to burn up the remaining time on the clock without risking a turnover or injury.

Receiving
While quarterbacks are mainly not a factor in terms of receiving forward passes, some trick plays, like the flea flicker, require quarterbacks to catch a lateral by a wide receiver or running back before delivering a forward pass. In the wildcat formation, a quarterback lines up as a flank receiver who can be used to catch a forward pass. Typically the quarterback is not thrown to in this formation, but serves as a decoy, as even the least mobile quarterbacks are capable of catching a ball for positive yardage. Occasionally, some backup quarterbacks may be used to receive long snaps as a holder for field goal or extra point attempts, as quarterbacks generally have good ball handling skills, and may have to become the quarterback in the event of a bad snap, an aborted kick attempt or a designed trick play.

Under NFL rules, if a quarterback lines up under center, he is by definition ineligible and not allowed to receive a forward pass. However, in college and high school ball, quarterbacks are eligible receivers (by a special exemption in the high school rule books) regardless of whether they are under center or in a shotgun formation. The NFL allows a quarterback in a shotgun formation to receive a forward pass.

Dual-threat quarterbacks
With the rise of several blitz heavy defensive schemes and increasingly faster defensive players, the importance of a mobile quarterback has been redefined. While arm power, accuracy, and pocket presence – the ability to successfully operate from within the "pocket" formed by his blockers – are still the most important quarterback virtues, the ability to elude or run past defenders creates an additional threat that allows greater flexibility in the team's passing and running game.

This is generally more successful at the college level. Typically, a quarterback with exceptional quickness is used in an option offense, which allows the quarterback to either hand the ball off, run it himself, or pitch it to the running back following him at a distance of three yards outside and one yard behind. This type of offense forces defenders to commit to either the running back up the middle, the quarterback around the end, or the running back trailing the quarterback. It is then that the quarterback has the "option" to identify which match up is most favorable to the offense as the play unfolds and exploit that defensive weakness. In the college game, many schools employ several plays that are designed for the quarterback to run with the ball. This is much less common in professional football, except for a quarterback sneak, but there is still an emphasis on being mobile enough to escape a heavy pass rush.

Two quarterback system
Sometimes a team is undecided on which quarterback should start a game. In that case, the team may employ alternating quarterbacks. This could have negative effects on the cohesion and consistency of the offensive team, but could also serve to confuse the defense. A rare successful example of a two-quarterback system can be seen in the "WoodStrock" combination of Don Strock and David Woodley, which took the Miami Dolphins to the Epic in Miami and Super Bowl XVII the following year (but did not win either game).