Cornerback A cornerback ( CB ) ( also referred to as a corner ) is a member of the defensive back field 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 .