If you’re a pro, then you know coaches.

Coaches who you could engage on friendly terms to say “Hey, can you coach my kid? And if needs be, let him down gently?” - see what they think of his potential, and if they need to be the one to tell him he is unlikely to make it, then it’s going to be easier coming from then than from his own Dad. You get to look like you’re backing him by sending him to “one of the best coaches in the business” and then console him when they deliver the rough news…