This poster makes an important point, but first, I agree with those who think communication is very important throughout the selection process. If I were the coach, I'd probably have anyone in contention race for it, assuming there is sufficient time for recovery. One earlier poster might be correct that the winner of the run-off might not perform the best in the state meet, but it's the only fair way, and you can't predict that.
The more important point in all this, as this poster points out, is that a time comes when parents have to give their kids some room to deal with their own problems. The situations we might imagine in this regard might be far different, but this is sport, and the kid is 17 or 18 years old. It's an ideal situation for him to learn to deal with an adult authority figure on his own in a fairly benign situation. That's a very important and valuable experience. A year from now, his parents are not going to be able to take up his cause if he wants to dispute a grade with a professor, and a few years from now, his parents can't shield him from a problem with his boss.
I wish the coach and all his athletes well.