considerably as a ballcarrier or receiver, not just a blocker. On defense meanwhile, an opposite philosophy to position naming is sometimes followed from that of the supposed third offensive end. Instead of the position name following the player to a different position, a new position name may be applied in such a substitution situation. This occurs when a team that usually uses four defensive backs (counting cornerbacks and safeties) adds a fifth, thus producing the "nickel" defense (a nickel being a 5 cent piece). It will be said that the extra DB is the "nickel back", even though coverage assignments will be redistributed, and therefore no particular DB is functionally or positionally in a "nickel" position, distinct from the other four. Nor, if a sixth DB is added, could one distinguish between the "nickel" and the "dime" back. However, if they are subbed in one at a time, an observer may apply "seniority" in naming one "nickel", etc. A roster will usually simply list such players as S, CB, or simply DB. See also History of American football References External links NFL.com's Pat Kirwan discusses the different personnel groupings that NFL teams use Canadian football History of American football