Re: I was wrong about....
I just remembered a pretty big one: Cueto.
He and Volquez were exciting up-and-comers around the same time, and I was positive that Volquez would turn out to be the ace and Cueto would be around a #4-type pitcher. I think it's still too early in their careers to guarantee that both of them will always be the type of pitchers they are now, but pretty safe to say I was very wrong on this. I thought Volquez had better stuff with a higher ceiling and that Cueto's build was going to limit him.
There is no such thing as a pitching prospect.