What must occur before a substitute can legally enter the game?

For a substitute to legally enter the game, the match must be stopped by the referee. This is a fundamental rule in soccer to ensure the game is managed fairly and safely. Stopping the game allows for proper management of the substitution process, ensuring that all players are aware and that there is no disruption to the flow of play.

Once the game is halted, the referee is able to acknowledge the substitution, allowing the player coming off to exit the field and the new player to enter. This procedure helps maintain the integrity of the match and ensures that substitutions are conducted in an orderly fashion.

Other options do not align with the rules governing substitutions. For instance, a neutral position for both teams is not required, nor is it a necessity for the referee to be given the ball before a substitution can occur.