While Peterson would probably be the best pitching coach the Brewers have had since Mike Maddux left town, how much could we possibly expect him to improve the pitching staff? In order for Peterson to work his magic, he has to have some talent to work with -- outside of Yovani Gallardo, Manny Parra, and arguably Dave Bush (I remain a fan of Bush's...that curveball is just too pretty when everything's clicking), there isn't much to work with. Peterson and Willie Randolph lost their jobs with the Mets largely because the pitching staff was a mess -- while Peterson was able to work out a couple of Perez's kinks, the lefty was still inconsistent under his watch (of course, since Peterson was fired, Perez has completely fallen off a cliff...take that for what it's worth).
Bill Castro was lauded for his performance when the team was pitching well in the early months of the season. When injuries and regression to the mean caught up with them, suddenly Castro was constantly criticized and eventually fired. Chris Bosio was praised for his work with Manny Parra in Triple A when Parra returned to the big league club with a string of very strong starts. When Bosio became the big league pitching coach and Parra struggled with the rest of the team, his performance was criticized. The front office currently claims that Bosio will have a fair chance to interview for the full-time job this winter, but if there's any validity to this rumor, it appears as though Bosio will also be shown the door.
It's the natural cycle of things for pitching and hitting coaches in the majors. They're easy targets despite the fact that they don't have much to do with the performance on the field. The top flight coaches -- those like Peterson or Dave Duncan -- do seem to have a small effect on a few pitchers, but rarely are the results sustainable. We've seen this first hand with how Jeff Suppan and Braden Looper have fared after learning under the "genius" of Duncan in St. Louis.
Could Rick Peterson have a positive effect on the Brewers' pitching staff? Sure. If he's the next guy to hold the job, I especially hope he can teach Gallardo and Parra to stop trying to strike everyone out, which in turn leads to less walks. But don't expect him to work miracles with the piles of stale crap that are Suppan and Looper (if he returns). Even if the Brewers hire Peterson, the pitching improvements cannot stop there. Doug Melvin & Co. still need to find a way to add depth, otherwise they'll be right back to square one next year the minute someone gets hurt.