My preference for groundball pitchers has come up a few times over the winter, most recently in discussing Clint Nageotte's likelihood of having a successful Major League career. Some people might look at his peripherals and declare that the odds are stacked against him, but the truth of the matter is that groundballers are able to get away with worse rates than the rest of the league. It's not real hard to figure out why, either - when you eliminate home runs, your ERA takes a plunge, even if you're walking a few more guys than the average. It's why I've taken a shine to Clint Nageotte, Jimmy Anderson before him, and Dan Reichert before him.
To illustrate the point, I'm going to use the run values given in The Hardball Times Baseball Annual 2006. Buy the book. Hell, buy several books. Go on a diet for a month, and spend the money you save on copies for yourself and your entire extended family. It'll make you physically and intellectually healthier, unless you're already dangerously thin, in which case you can just spend all the money you have on books and eat the ones you don't read. Anyway, the run values are listed as such:
Groundball: +0.101 (for pitchers)
Outfield fly: -0.035 (almost entirely due to HR factor)
Looking at those numbers by themselves is probably enough, but let's try to drive the point home a little bit by examining two hypothetical pitchers, Pitcher A and Pitcher B. The two guys are identical save for the fact that Pitcher A has a 3.99 GB/FB rate (highest in the league last year, per THT) while Pitcher B's is 0.65 (lowest in the league, same reference). Assuming equivalent peripherals and 500 balls in play for each, Pitcher A can be expected to allow approximately 28 fewer runs than Pitcher B. A difference of nearly three wins, simply by occupying opposite sides of the GB/FB spectrum. For perspective, that's like swapping out 2005 Joel Pineiro with 2005 Scott Kazmir.
In reality, the difference isn't quite that large - evidence has shown that flyballs are more costly for groundball pitchers than they are for flyball pitchers, suggesting that the "11% HR" rule should be altered a little bit for different pitcher types. So anyway, let's take a look at the performance of the top- and bottom-20 GB/FB pitchers from a year ago:
Their walks are identical and the second group actually has a better strikeout rate than the first, but the groundball pitchers still have a 32-point advantage in FIP and 75-point advantage in xFIP. Over 200 innings, that's a difference of anywhere from 7 to 17 runs despite missing fewer bats. To me, that's pretty significant. The flyball pitchers are able to exceed their xFIP's by virtue of (A) having slightly greater control of their outfield flies than groundballers, and (B) allowing more catchable balls in play (fly balls are fielded more often than groundballs), but you're still talking about a difference of a win or so, from one slot in the rotation.
If Clint Nageotte is able to remain a fairly extreme groundball pitcher, he won't need to improve his control all that much to become a viable ML starting pitcher. Dan Reichert managed an FIP in the low-5's despite a high walk rate and a K/BB around 1.00; Nageotte could hover in the mid-4's simply by elevating Reichert's strikeout rate, which probably wouldn't be much of a problem given enough innings. And with improved control, he could be much, much more.
I'll repeat what I said in my last post: right now, Clint Nageotte is not ML-ready, but I think there's a pretty good chance that by 2007, he'll be ready to assume a full-time #4/5 rotation gig. And it's not because of the stuff and results he flashed in the low minors, either - it's because he's become a fairly extreme groundball pitcher, and it's pretty hard to suck when you have that kind of ability.
If you're a parent, start teaching your son from an early age to throw a sinking fastball with his left hand. 20 years later, it'll pay off bigtime.