In American football

American football

American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...

, a nickelback is a cornerback

Cornerback

A cornerback 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...

 who serves as the fifth (in addition to the typical four) defensive back on the defense. A base defense contains four defensive backs, consisting of two cornerbacks, and two safeties. Adding an extra back makes five, hence the term "nickel", which is the name for 5-cent coins in the United States and Canada. Usually the nickelback will take the place of a linebacker, so if the team were to be in a 4–3 formation, there would now be four linemen, only two linebackers and five defensive backs creating a 4-2-5 formation. However, some teams will replace a lineman rather than a linebacker, creating a three linemen, three linebacker and five defensive back alignment, a 3–3–5 formation. If an offensive team always uses three or more wide receivers, a defense may turn to a nickel defense for their base package on most plays. Usually extra defensive backs, such as a nickelback, are substituted into the defense in situations where the opposing offense is likely to attempt a forward pass, such as 3rd-and-long, or when extra receivers are substituted into the opposing offense.

The nickelback is the third cornerback on the depth chart. The nickelback is not considered a starting position because the starting formation for a defense has only two cornerbacks. Defensive formations with four or more cornerbacks are used often enough that a nickelback will usually see moderate playing time (particularly in the modern, pass-oriented NFL) as well as subbing in for the starting corners.