Why would a coach wish to project a substitution between a catcher and a left fielder?

The rationale for a coach projecting a substitution between a catcher and a left fielder primarily revolves around the strategic advantage of utilizing a courtesy runner for a slower player, particularly when that player reaches base. In baseball, the rules permit a team to allow a player who is considered a slower runner—such as a catcher— to have a courtesy runner. This strategy is particularly advantageous in high-pressure situations where the team is seeking to maximize potential scoring opportunities while maintaining the integrity of the lineup.

By substituting the catcher for a left fielder, the coach can effectively put a faster runner on the base paths, which broadens the team's offensive capabilities. The essence of this decision is to enhance the chances of advancing bases, stealing bases, or scoring, which can be pivotal in tight matches.

This choice specifically allows the team to maintain an effective defensive lineup while also optimizing offensive play, showcasing the duality of tactical decisions in baseball. Other options, although potentially viable in different contexts, do not serve the immediate need for increasing the effectiveness of the running game when a slower player reaches base.