The problem is with out potential any player can be coached/trained into the Hall of Fame which just isn't realistic. The fact is almost all players won't reach that level and no amount of coach, training, whatever will change that.
This works great for made up players. The problem you are saying is that is prevent the existing players from developing into player they could wind up becoming.
There is not miracle solution to that dilemma. There are two choices:
- All existing players have a 99 potential
- Someone (In this case Donny) guesses as to what the future will hold for these players based on the information he has at hand
I have to choose option 2. in this case because no one can see into the future and I wouldn't want to see all these player have that much potential because that is further from realistic.