Former Louisiana Soccer Technical Director and former Technical Director of US Youth Soccer, Sam Snow, authored a comprehensive treatise on player development. It outlines the philosophy and best practices of player development. It also accurately reflects the prevailing attitudes world-wide not only of soccer professionals, but also of childhood development experts.
Youth players start to leave the game at age 9, before they have had the change to fully grow physically and cognitively. The reason most cite for leaving is that it stops being fun and overwhelmingly the reason the game stops being fun is some aspect of adult behavior. In fact, 7 out of 10 players leave the game before they turn 14!
To reverse this trend clubs, coaches and parents must understand the key elements of player development and must focus their programming entirely on those elements.
To read Sam Snow's treatise on player development