What is the standing of an illegal substitute discovered at bat?

When an illegal substitute is discovered while at bat, the ruling is that the illegal substitute is considered out. This is in accordance with rules governing player substitutions in many sports, ensuring that the integrity of the game is maintained. The immediate action taken in this situation emphasizes the importance of adhering to rules regarding player eligibility and proper substitutions.

By declaring the illegal substitute out, it upholds the competitive fairness of the game, as substitutions must be tracked accurately to ensure that teams are fielding the correct players. Other scenarios, such as continuing play without interruption or pausing the game for a ruling, would not address the violation of the substitution rule as effectively. Likewise, simply replacing the batter does not adequately penalize or rectify the situation regarding the illegal substitute status. Hence, the ruling that the illegal substitute is declared out is the most logical and enforceable course of action in this context.