Dayn Perry at Baseball Prospectus looks at the minor league pitching careers of good and bad major league pitchers and finds little difference in quality, but that the bad ones spent more time in the minors. In short, a study that raises more questions than it answers. He notes that he excluded late-career returns to the minors, but I can’t shake the feeling that some of the bad ones had good numbers because unlike the good ones, their subpar stuff kept them in the minors after they’d learned how to pitch.