How to force u19 team to start a player?

I have a 15 year old that will be a star. Unfortunately he is not very good now and he is never chosen to play in his U19 team.

Can this be done??

I think the team manager picks the best player for each position if available.

At 15 though, I would probably leave him training and not worry too much about u19 game time for a year or so.