Is it always necessary for a substitute to enter the field of play for a substitution to be completed?

In soccer, a substitution is completed when a substitute actually enters the field of play, and the player being substituted leaves the field. This is in accordance with the Laws of the Game, which state that the replacement of players requires the substitute to step onto the field and the outgoing player to exit it. If a substitute does not physically enter the playing area, the substitution is considered incomplete.

While there might be specific circumstances in some formats or informal games where a player might momentarily leave the pitch without a formal substitution process, the standard rule upheld in official matches is that for a substitution to be valid, the incoming player must fully enter the field of play. This ensures clarity and fairness in the match, as it allows for appropriate match management and the correct number of players on the field at all times.