Here is an short video clip about the manager of the Grand Prairie AirHogs (American Association) during an open independent pro baseball tryout right before spring training:
The reason tryouts often are held just before spring training is that, surprisingly, a player sometimes “no shows” spring training. Other reasons include looking at possibly-overlooked talent, needing a spring training “filler” player if a player is going to report to spring training but might need more time to heal from an injury, etc. If you attend an open minor league baseball tryout right before the spring training starts, do not despair. You actually may get a better look and be on the “short list” should there be a need for depth at that position later in the season.