Broad, you say this boy (or man-child, as you put it) is "a bigger, stronger player" than the others on that team - is it possible that he is also "better" than the others? If all he has going for him is strength and speed, that will be discovered quickly enough and he will spend his share of time on the bench.
You could choose to make this, or similar situation, into a "life-lesson" kinda thing. There is always going to be someone bigger, better and badder than you – the sooner a person learns this fact of life, the better. No one wants to see their child go through any kind of pain, but times of difficulty can often make you a much stronger person - emotionally and physically; doesn't always, but it can.
Playing in the Premier League is a big step up from Challenge League. I have always felt that bringing in a better player, or more (whether it be only for training, or to actually join) can only help a team (and I'm not talking about their record). That player can immediately raise the bar for the entire team, and will fairly quickly show you what types of players you have. The ones who should be in that league will work harder and prove that's where they need and deserve to be; the others will essentially give up and/or spend their time complaining about how unfair things are.
How you as a parent react to and address this type of situation will probably affect your child much more than the situation itself.
