As far as the main thrust of the thread goes, the biggest thing for me is that the absolute rule is prospects fail. I find it much easier to frame understanding of a prospect's chances when you understand that the default is not how successful the player will be, but if he will ever even spend a day on a MLB roster. With that in mind, I think of performance/stats as the engine that powers a player to whether or not they can reach a potential that scouting information puts on them. People like to point to the exceptions to show why you shouldn't scout a stat line, but I've never seen compelling info that there's more of those than the reverse, where scouting undersells a guy's potential(Donaldson, Matt Carpenter, Hendricks, etc). Or in other words, there's more all-stars that never made a Top 100 list than there are all-stars that couldn't hit(or strike people out) in AA.