I think a potential (pun intended) solution to the problem would be to give players a label based on their current skills.
Current Ability: Starter
Potential Ability: MVP
I think it might also be a good idea to decrease potential on players that are not getting trained. If I have an 18 year old HOF sit on my bench and not get training for 3 seasons, he will never been able to get to his HOF potential. I think both of these things would help prevent new players from overspending on potential.