Over the last few weeks there have been a series of debates about whether pitchers like Neftali Feliz and Madison Bumgarner are stronger than pitchers like Jhoulys Chacin and Derek Holland. Most people seem to think that Feliz and Bumgarner are stronger prospects, but the question of just how much stronger they are has been fought bitterly. 

A number of people have tried to argue that Feliz and Bumgarner's success at lower levels should be downgraded because they rely primarily on their fastballs. They say that considering you can't rely strictly on a terrific fastball at the higher levels, therefore they will face more difficulties than Holland and Chacin who have better secondary stuff. 

Intuitively, this seems sensible but I'm wondering if it's true. Considering none of these pitchers (with the arguable exception of Holland) have had consistent, outstanding success at AA or higher levels, it seems like they all have to improve a lot. Those people seem to be arguing that a pitcher with a good fastball and a decent breaking ball in the low minors is more likely to become a good major league pitcher than one with a terrific fastball and an uncertain breaking ball. 

I have a problem with this argument on a number of counts. First, if Holland's and Chacin's secondary stuff were as strong as some seem to believe, then it should show up in their stats. They should have blown A ball hitters away at the same rates that Feliz and Bumgarner do; I don't understand why an A ball hitter is supposed to be decimated by a terrific fastball, but not by a terrific curveball. Second, pitchers with as good fastballs as Bumgarner and Feliz might be able to get away without an excellent breaking pitch even in the majors; certainly they'll need a good or even a decent breaking ball, but their secondary stuff probably doesn't have to be as strong as Chacin's or Holland's would. 

I'm wondering what other people think; are there any pitchers like Feliz and Bumgarner in the past? Did their secondary stuff develop or did they flail in the higher levels?