A priori reasoning is a fancy way of describing reasoning based on theoretical deduction rather than empirical observation.
Let's do our best to move away from a priori presuppositions in our youth soccer environment.
Allow me offer a few examples.
"My son can play division one soccer. I have not been to a division one game or training session in a long time, but I played division three. I know enough to know that my son has what it takes to play division one."
"I watch professional soccer games on television. At the highest level, they are good, but I am good enough to play for a bottom half team in France or Germany".
"My son is not playing consistently, the coach has no idea what he is doing. He has it out for my son."
"You are not tall or physically strong, you can't be successful at central defender. Even though you want to play there, and we don't have a designated player for that position, I don't think you will have success there."