Cornerback



A cornerback (CB) (also referred to as a corner) is a member of the defensive backfield or secondary in American and Canadian football. Cornerbacks cover receivers, to defend against pass offenses and make tackles. Other members of the defensive backfield include the safeties and occasionally linebackers. The cornerback position requires speed and agility. A cornerback's skillset typically requires proficiency in anticipating the quarterback, backpedaling, executing single and zone coverage, disrupting pass routes, shedding blockers, and tackling.

Overview
The chief responsibility of the cornerback is to defend against the forward pass. The rules of American professional football and American college football do not mandate starting position, movement, or coverage zones for any member of the defense. There are no "illegal defense" formations. Cornerbacks can be anywhere on the defensive side of the line of scrimmage at the start of play, although their proximity, formations, and strategies are outlined by the coaching staff or captain.

Most modern National Football League defensive formations use four defensive backs (two safeties and two corners); Canadian Football League defenses generally use five defensive backs (one safety, two defensive halfbacks, and two corners). A cornerback's responsibilities vary depending on how the defense assigns protection to its defensive secondary. In terms of defending passing plays, a corner will be typically assigned to either zone or man-to-man coverage.



Zone coverage
In zone coverage, the cornerback defends an assigned area of the field. Many schemes and variations were created to provide defensive coordinators great latitude and flexibility which aim to quell offensive schemes.

When utilizing zone coverage, some areas of the field require special attention when defending against specific pass plays. They include the flats (to defend the screen pass and hitch routes), mid range zones including the void (to defend the "stop n go," quick post, fade, hook, curl, and "sideline" or "out" routes), and finally the deep zones (to defend the post/deep post, chair, streak, "fly", "go," bomb, or Hail Mary routes). These are basic terms (perhaps the most generic) for the basic zones and routes which vary system to system, league to league, and team to team. Advanced forms of coverage may involve "quarterback spies" and "containment" coverages, as well as various "on field adjustments" that require shifts and rotations; the latter usually initiated by the captain of the secondary (typically the free safety) during the quarterback's cadence. At this time the captain attempts to "read" the alignment(pro set, split set, trips, etc.) of the offensive "skill players" (backs and receivers) in order to best predict and counter the play the offense will run. He will base his decision on past experience, game preparation, and a sound comprehension of his teammates strengths, abilities, and tendencies. These adjustments may change on a play by play basis, due to substitutions or even evolving weather or field conditions. For example, defensive coordinators may favor a tendency to play a less aggressive containment style zone coverage during wet or slippery field conditions to avoid problems associated with over-pursuit (when a defender takes a poor angle on a ball carrier and cannot redirect in time due to poor footing).

Cover 2
The Cover 2 (Two) is popular among defensive coordinators in the National Football League because it implements two safeties to defend the deep routes instead of one. This coverage allows the safeties to watch the play develop in front of them thus allowing the corners to pursue a more aggressive style of play. Cover 2 is a "2 Deep Zone" that uses 4 defensive backs. Two safeties line up deep, around 11-15 yards off the line of scrimmage (usually each safety stands on or a few feet from his hash mark), while the cornerbacks line up around 5 yards from the wide receivers which are nearest to each sideline. In Cover 2, the cornerback is usually responsible for "containment". This is where he does not allow anyone to run outside of him (between him and the sideline). He then funnels or jams receivers towards the middle and within 5 yards, reads the quarterback, and finally drops back to defend the void if there isn't a throw to the flat or a running play. Typically with the Cover 2, cornerbacks mirror each other's zone responsibilities. However, sometimes they play a "man-up" style bump and run, a form of bump and run designed to eliminate the short pass, where the receiver is forced to the near sideline, which is the opposite of the run oriented "containment" style of Cover 2. Usually if one corner is in man to man coverage, the other is in man to man coverage as well. The two safeties act as a security blanket for deep routes.

Cover 3
In a "Cover 3", the two corners and free safety defend their assigned deep thirds of the field, where the corners defend the outside third, (hence the term corner) while the safety defends the middle third. This allows the strong safety to address a full range of duties depending on what reads he makes coupled with the coverage called. These duties may simply include single or zone coverage, being a quarterback spy, providing extra run support in short yardage situations, or to stunt or blitz through a gap or from the end.

Cover 4
In a "Cover 4" each defensive back is responsible for covering his designated "deep fourth" of the field, while other defensive players are responsible for covering the underneath areas. Sometimes Cover 4 is used as a "prevent defense".

Variations of these coverages exist to counter the many styles of offenses a defense may face on any given week. For example, one variation of the Cover 2 allocates the weak-side corner (e.g.: typically the "right cornerback" when playing against right-handed quarterbacks) to cover half the field in order to free up a safety; the idea being to allow the safety to engage a different part of the field, blitz, contain, or spy. The strong side cornerback (the "left cornerback") may be in a variety of different alignments which may include "loose man", "man-under", or "man-up". Although these are forms of single coverage, more often than not his responsibility is usually limited to an initial jam and funnel with a subsequent drop back into the "void". This pie-shaped slice of field is included with your most basic 2 Deep Zone coverage. One interesting aspect sometimes encountered with Cover 2 is that it's possible for one corner to be in a zone coverage, where he funnels and drops into the void, while another may be in man coverage. However, your basic garden variety 2 Deep Zone usually employs the two safeties to share half the field responsibilities, with the two corners funneling.

Jamming the receiver
When a cornerback is attempting to jam or funnel a receiver, he is trying to disrupt the receiver's route at the line of scrimmage. By impeding the receiver's progress, the corner can provide his teammates with extra time to sack the quarterback (sometimes called a "coverage sack"), or force an ill-timed throw. In addition, a proper jamming allows the safety or linebacker to provide stronger run support because he then has more time to drop back into zone coverage in the event of a pass. In other words, he has been granted more time by the corner to recover from his mistakes if he anticipates a run when in fact the play is a pass.

If the jam fails, the cornerback is usually flat footed and not in a suitable position to defend the mid to long-range passes. When this occurs, the safeties and linebackers usually cannot return to their zone obligations in time, especially if they were anticipating a run as the play began. In essence, the defense is unnecessarily "stretched" to its breaking point. Receivers who can effectively avoid the jam and stretch defenses are far more likely to create big play opportunities for the offense. Therefore, it is vital that a cornerback execute a proper funnel or jam to allow safeties and linebackers enough time to return to their zone responsibilities in the event of an unforeseen pass play. By working together and familiarizing where one's help may come from, a higher degree of confidence is established amongst the defensive secondary as a unit, with the end result translating into a much more formidable defense against both the run and pass.

Single/man-to-man coverage
In single or man to man coverage, the cornerback is responsible for a particular receiver assigned to him. As the play begins, the corner may either attempt to "jam" the receiver at the line, play a step or two off of him, or concede a few yards and play with a "cushion". Cushions can range from a yard or two, to forty yards in a "prevent defense" situation. Cushion is just a term used to describe how far off the defender plays away from the offensive player he is assigned to defend. Generally, cushions are smaller in single coverage and larger in zone coverage.

Single coverage in the "red zone" (an area between the goal-line and the twenty-yard line) is usually designed to prevent receivers from slanting towards the middle of the field. These types of routes are difficult to stop in the red zone because this area is usually congested with bodies colliding, crossing, and weaving in different directions. Although illegal, defenders are easily picked or screened (this is illegal yet hard to enforce in short field, congested situations) by opposing receivers and sometimes by their own teammates. To avoid this, it is often favorable for cornerbacks to either: "switch" assignments (where he will agree beforehand to trade assignments with one of his fellow defenders in the event that the receivers criss-cross as the play begins), or alternatively, a corner may instead line up close enough to the receiver (very close) at the line of scrimmage to force or jam him  toward the sideline (outside) without violating the 5 yard no touch rule. Corners often refer to this second style of coverage as the "man under" technique.

Single coverage, or man to man coverage usually employs relatively few techniques. However, they are often initially displayed to resemble one another as much as possible to disguise the true motives of the defense, and be interchangeable as well. Although terminology for single coverage can vary, a few generic terms have been included to establish a general understanding of cornerback philosophy and how his function relates to the rest of the defense.

Man under
This man to man technique is very similar to the man up technique described below except there isn't a free release. The corner usually attempts to force the receiver toward the near sideline and jam him in order to prevent him from running toward the inside or middle of the field. To do this, the corner lines up as close as possible to the receiver without being penalized for being offsides. This coverage is used in goal line situations, as well as when a blitz is called. During this coverage, the corner doesn't have anyone to help him cover the receiver if he runs inside because his usual help is blitzing or in single coverage as well.

Loose man
Loose man requires cornerbacks to play off the receiver with a five to ten yard cushion. He usually doesn't touch the receiver and tries to keep his head on a swivel while remaining indifferent upon which direction the receiver decides to shape his route. Typically with loose man coverage, the cornerback has little or no help from the safety in defending against the receiver.

Man up
By far the most challenging, the man up technique grants the wide receiver a relatively free release as the corner shadows him stride for stride everywhere he goes. The cornerback's objective here is to position himself between the quarterback and the receiver, without knowing where the receiver is going. As the ball is snapped the corner will initially ignore the quarterback, turn and run with the receiver and hope the ball doesn't drop out of the sky before he can react to it. Corners must also hope the receiver doesn't change directions when it's time to sneak a peek at the quarterback in effort to discover where the ball is. A wet field makes this coverage extremely difficult. In addition, a perfect throw is hard to if not impossible to stop. This coverage is reserved for the elite cornerback as it is in this coverage where corners are most frequently beaten.

"Shutdown corner"
The term "shutdown corner" defines a cornerback who is so good at his position that he "shuts down" an entire side of the field. The term has been liberally applied to many cornerbacks, though the rules on contact with receivers have made it less common in recent years.