Here is my grading scale for prospects 1-25. I choose a grade and it show what I think they will become.
Surely going top be the best player in the game.
Going to be a star.
Probably going to be a star
A great player. Maybe a star.
A chance to be a star, probably will be an average player.
Has potential, will probably be a solid player.
Might never make it, has potential, Above-average at best.
Average at best likely a middle reliever or a bench player.
50-50 percent chance they make it. If they do probably a pen arm or bench player.
Not likley to make it to MLB, not going to be a starter. Not worth much.