This reminds me of a friend of my sons, they played youth football together.
He was a stud in that 5th grade to 8th grade range. Started at DE or OLB, was the back up QB, played WR, was the kicker and punter as well. Literally played every down of a game. Made all stars teams every year ect. He was taller and bigger than most of the boys and actually had muscles. By the time freshman year of high school came around he was still starting, but just on defense and would rotate in at OT at times. Sophmore year came and he was a back up defense, junior year playing only kick coverage. He quit after his junior year.
What happened? Puberty basically. He was bigger and stronger when he was young....had whiskers at 12. The playing field level when the other guys caught up to him. The biggest thing with youth sports, I would include high school in this as well....enjoy the experience, have fun, make friends.
This boy, being a good kid and bigger/stronger than most would stick up for my son when he went through a period of getting picked on a bit one school year.
My son and this kid are still friends. They are in college now. My son used to come up to his chest freshman year of high school and now he is 3 inches taller. They are going sky diving later this month 
. Those youth sports friendships and experiences can really mean a lot to kids growing up, that should be the focus in my humble opinion.