One more thing you need to be aware of is this:
Look at projections, but also current ratings. Your projections will be off on the high side, as others have said, and you can use current ratings as something of a guide to how far short of projected ratings a player will fall...
The older a player is, the less he will progress as a professional, and so college seniors need to start considerably closer to their projections than HS players, and so on. If your gut tells you that a players will fall way short of projections, you're probably right.