A cornerback (CB) 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…..with other members of the defensive backfield including the safeties and occasionally linebackers.
The cornerback position requires speed and agility…..with a typical skillset requiring proficiency in anticipating the quarterback….backpedaling….executing single and zone coverage….disrupting pass routes….and block shedding….with the chief responsibility of the cornerback being to defend against the offense’s pass. There are no “illegal defense” formations….so, 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.
The most effective cornerbacks are typically called “lockdown corners”….because they can cover an offensive receiver so effectively that the quarterback does not throw towards (or target) the receiver being covered by a “shutdown corner” any longer…..making a “shutdown corner” is typically used to refer to only a few elite players.