Tailback

Tailback is a backfield position in American football referring to the running back who lines up furthest from the line of scrimmage in certain formations. The tailback is typically the primary ball carrier, though responsibilities vary by scheme; in some systems the backfield includes a fullback who blocks and short-yardage, while the tailback handles rushing, receiving, and pass protection.

Historically, tailback terminology arose to distinguish from the fullback, who lines up closer to the line and often serves as a blocker or short-yardage runner. In many older formations such as the single-wing and early T-formation, the tailback took on the main rushing duties. In modern offenses, the term is used less frequently; players are commonly called running backs or RBs, with roles categorized as primary runner, receiver, or versatile back.

Skills for the tailback include vision to read defensive fronts, speed and agility to evade tacklers, and competence as a receiver and blocker. The position requires versatility, as tailbacks may be asked to run between the tackles, outside, catch passes out of the backfield, and provide pass protection on blitz plays.

Other uses: the term tailback also appears in traffic engineering to describe a queue of vehicles extending backward from a bottleneck, which is unrelated to football.