Do you pick on training standards or Saturday performance?

I would make both things matter and be clear about how. Training standards should influence selection because they are part of the team environment. Effort, reliability, response to coaching and how a player works with teammates all tell you something. But I would not pretend Saturday performance is irrelevant either. The key is avoiding surprise. If the matchday player coasts all week and still starts every game, the squad learns that training standards are optional. If the excellent trainer never gets meaningful chances because their match form is inconsistent, they eventually stop believing training can change their position. I’d explain the criteria before the issue becomes personal. At U15, selection can start carrying more consequence, but it should still serve development. Sometimes that means starting the player whose weekly standards deserve the opportunity and giving them enough time to show whether those habits transfer to the match.