Or more expanded based on knowledge?
And should the parent try to grow their own knowledge?
A parent would only need to support what the coach is asking player to do.
LOL wouldn't actually have to think for themselves.
Just support the coach to try and get the kid on board with some sort of discussion regarding having the discipline to apply what the coaches trying to get them to do.
When my daughter decided to take ballet classes at the age of 6, my wife did what she could to help her. I simply don't have the grace required for such an activity, and I doubt I ever will no matter how much I learn.
When my daughter decided to get involved in sports, that is when I stepped up. My focuses with her were hitting and fielding, and to this day she will still ask me questions. Her college coach may make a comment about her mechanics and I will decipher it for her, not only to help her, but also to support her coach (as you are saying). She has a private instructor for pitching, and I try not to get involved in that. However, I attended the lessons and tried to pay attention as much as I could. Then when I notice something or see that look on her face, I simply say "what would your pitching coach tell you?". In those cases I may not be the one providing instruction but I am still supporting her and supporting what her coach says.
My point is that I will support my daughter as much as I can, but that doesn't mean I am able to teach her a specific topic. In some cases I have to rely on the talent of the instructor and do my best to support that instructor. I'm sure I am not alone in my thoughts, but I'm equally sure that there are parents that would rather not get that involved.