How do you edit the primary position of a player in NBA 2K9? I want my Joe Johnson to permanently be an SF.?

In ociation, the current team that I'm using is the Miami Heat. I traded Shawn Marion for Joe Johnson because I was having difficulty with his shot. :)) Anyway, my line up turned out to be Joe being on the bench because he's an SG so now he's backing up Dwayne Wade. I want him to be an SF. Permanently. I know that I could change the starting line-up but once Joe goes to the bench, he never comes back. I don't want turn off the auto sub option. Help please. :D