What about this scenario: Before say a coach from a large club was able to take guest players to big tournaments, kinda look over the players and then if that player turned up at tryouts the next year they would then have a pretty good idea of how the new player performed. Without utilizing that player as a guest for a tournament, then all the coach might see of the player is the limited one or two nights at tryouts. Without seeing that player in a real competitive environment the coach might A; not pick the player since they do not know how they are likely to perform; or possibly B; pick the player only to discover later that the player can not cut it with the rest of the team. Lets just say B occurs; Player leaves his first club,where maybe he/she was a star only to join a new club and then the following year he is relegated to a lower team.
