What is a substitution in football?

A substitution happens only during a stoppage in play and with the referee's permission. The fourth official raises the board showing the numbers; the leaving player exits at the nearest boundary line, and the entering player joins from the halfway line.

Only players named on the match squad list may come on, and a substituted player cannot return in the same game. Every change is therefore irreversible, which makes it the most decisive in-match tool a coach holds.

The allowance has grown over time: three changes were the standard for decades, and five became permanent as fixture calendars grew heavier. To keep the game flowing, the five must generally be used across three stoppages, with half-time not counted as one of them.

Competitions that play extra time usually grant an additional change. Concussion substitutions sit outside the normal count in many competitions: player safety is not asked to fit inside a quota.

Fresh legs against tiring defenders show their worth most in the final half hour. A substitution does more than restore energy: paired with a change of shape, it can transform the whole game plan.

Timing is a craft in itself. Moving early hands the opponent time to respond; moving late wastes minutes. A defensive change made to protect a lead and a double attacking change made to chase one are two faces of the same rule.