Just goes to show how bad your "coach" can be at determining the best players for those positions. The code that determines that is definitely outdated and probably bugged in a way, so we'll try and fix it in one of the next larger GE updates. Until then, make sure you set all the positions manually for best results.
Is this first sentence also saying/implying that “Let Coach Decide” is potentially outdated and possibly suffering the same bug(s)?