Playing Time for Athletes

As a coach, I deal with a lot of requests, sometimes demands, from parents for playing time for their son or daughter. I remember the days that I spent on the bench in football. I don't however remember my parents asking for playing time for me. Instead, I was told to work harder and earn a spot. And no matter how hard I worked, I was too small for the sport...and yet, no request! Instead, I found track and summer league baseball. Two sports in which I could excel. I tried other sports, but I was on the bench in every other one.

So why do parents do this? Does it help or hinder the athlete? As a coach, what would you do to get this across (keeping in mind that the parents have signed a paper stating time didn't matter and may not have shown up at the sports meeting before the season began)?