What occurs when a coach sends out a courtesy runner but fails to report the change to the umpire-in-chief?

When a coach sends out a courtesy runner but does not report this change to the umpire-in-chief, the courtesy runner automatically becomes an official substitute without incurring a penalty. This means that the play can continue, and the courtesy runner is allowed to perform as a substitute for the original player. The key aspect here is that while communication with the umpire is important for maintaining the flow of the game and adhering to rules, the absence of a report does not nullify the change on the field. The courtesy runner fulfills the role intended without further consequence in this scenario.

The other options suggest various penalties or restrictions that do not align with the rule; for example, stating that the courtesy runner cannot play or suggesting that the original player cannot return would impose unwarranted consequences on the team based solely on the lack of reporting, which is not the case. This underscores the understanding that proper reporting is essential, yet not reporting does not retroactively alter the status of the courtesy runner regarding game participation.