What must occur before the completion of an infield play?

In the context of baseball, an infield play involves various actions that can impact the game's flow and outcome. The key requirement before completing an infield play is that all necessary legal conditions are satisfied, including the identification of eligible participants on the field. When an illegal player is discovered, it renders the play problematic, as it can affect team eligibility and compliance with the rules. Thus, identifying an illegal player must occur before executing plays to ensure that all participants are legally allowed to compete.

In this scenario, the discovery of an illegal player interrupts the regular flow of play and requires immediate attention from the umpire, making it a crucial factor before any inning's infield play can be officially counted and completed. The other conditions mentioned, such as signaling a timeout or requiring specific actions from the pitcher or coach, are not essential prerequisites for an infield play to be valid; they relate more to game management and procedures rather than the legality of the players involved.