What can I do to change my coach's mind about me (details inside)

I’m a junior in high school and have been on the volleyball team for the last two years. Although I’m not the world’s best player or anything, partly because I’m short, I’m a pretty decent passer. The last two years I, along with three of my friends, was one of the best players on the teams that I was put on. The coach never had a problem with me and always told me he saw a future for me in his program.
All of a sudden, this year the coach seems to think I’m absolutly awful, even though I’ve gotten way better every year! He put me on JV , while taking all of my friends up to varsity, even though there easily could have been room on varsity for one more. Some of the people he took up had exactly the same skill level as me in the position I was trying out for!
He told me I would be the first person he would bring up if he ever needed someone on varsity. Well guess what? When someone was needed on varsity in the position I play, he brought up a girl from the freshman team who is worse than me. I’m so offended and sad. I’ve had a great attitude the entire season, despite having to play at a level that is extremely low. Nothing I do seems to impress him, and no matter how well I play or how hard I try he still seems to think that I’m an awful player. I’m not an over confident person, but I KNOW he is underestimating me and he won’t even give me a chance. He refuses to acknoledge anything I do right! What should I do in this situation? Should I confront him in a polite way?