Who can discover an illegal substitute during a game?

An illegal substitute can be discovered by the umpire, the home team, or the visiting team because all parties involved in the game have a vested interest in ensuring that all players are legally substituted.

The role of the umpire is to enforce the rules of the game, which includes watching for any infractions, such as illegal substitutions. However, both teams also have the responsibility to be aware of the rules and the players on the field. Any member of either team can bring an illegal substitution to the attention of the umpire if they notice it during the game. This collaborative responsibility helps maintain the integrity of the game and ensures fair play.

This approach encourages vigilance from both teams and empowers them to actively participate in the enforcement of the game's rules. It also acknowledges that oversight can happen on any side, and thus any team can identify or challenge a suspected violation.