To the average fan, Matt Cain must seem like about the least controversial player on the Giants. He mostly keeps quiet to the press, doesn’t get arrested for having pot in his car. If he has any friends that look like participants in the Folsom Street Fair, we don’t see them on national television. But in the world of nerds arguing over statistics on the internet, Matt Cain is the most divisive Giant since Fred Lewis (and, yeah that’s pretty goddamn divisive).

What’s divisive about Cain can be captured in one fairly simple statistic: xFIP. This is one of those run estimators that is supposed to strip all of the things not under a pitchers control out of ERA. The idea is that three basic things that pitchers control are their walks, strikeouts and the number of fly balls allowed. Pitchers have limited control over how many batted balls fall in for a hit, how many oftheir runners they and their bullpen allow to score, and how many of their flyballs leave the yard. In the long run, a pitcher’s ERA should almost converge to his xFIP.

This Hair is the Key to a Low HR/FB Rate

The people who invented (and most of the people who use) such statistics admit that there is a certain amount of skill baby thrown out with luck bathwater in xFIP. Some pitchers can control their BABIP to an extant, and pitchers of a certain profile are more likely to strand more runners. These stats are designed to work better on average MLB pitchers, and there is a whole wide world of not average out there playing baseball.

Matt Cain may be the single active champion of not conforming to these well established theories of pitching evaluation. Matt Cain’s ERA is lower than his xFIP by a full run in over a thousand innings. That’s, well, abnormal. If you take xFIP at face value, you have to either think that Matt Cain is the luckiest man to ever hold a baseball, or that  he is the real freak in the Giants starting rotation.

How does Cain do it? Well, every way possible. He allows an unusually low number of HRs per fly ball. He also has a below average BABIP and is above average at what  base runners he allows. That’s three for three on the major “luck-influenced” stats can effect a pitcher’s ERA.

There’s no sense in giving a detailed summary of the debate over Cain’s HR/FB rate. Much of what has been written has done a better job than I could do. Here are the links for those of you contemplating majoring in Matt Cain Studies as an undergraduate:

• Paap-fly breaks down Cain’s statitical history, and mentions that this guy named Koufax was also able to harness the powers of the fickle HR/FB fairies.
• Dave Cameron responded that of the 10 pitchers posting 1000 IP of below average HR/FB from 2002 to 2007, only two maintained their previous rates over 2008-2010.
• Paapfly picks apart Cameron’s group of comparable pitchers.
• David Pinto posits that the lack of drop on Cain’s fastball induces pop-ups and weak flies.
• Crazycrabbers finds that drop on a fastball is negatively correlated with fewer HR/FB.
• Grant at MCC complains about naive use of xFIP in a letter postmarked to The Viceroy of Stats.
• Tom Tango grounds the debate in general methodology.

These articles summarize the situation nicely, and there are only a few loose ends worth tying up.

Cain is hardly alone in his xFIP defiance, he’s just the most extreme example. Jered Weaver, Chris Young and Adam Wainwright have all put up north of 700 innings with xFIP-ERA disparities of 0.67,  0.75 and 0.89. Like Cain, these guys all dwell in pitcher- friendly HR parks. They all have above average strikeout and pop-up rates, and all but Wainwright are decidedly fly ball pitchers.

I think almost everyone agrees that there exists some skill about keeping fly balls in the yard, and Matt Cain has it. The debate lines up as “Not Much Ability” versus “More Than Enough Ability”.  The  regression built into xFIP is rather crude, though. It expects every pitcher’s HR/FB ability to regress to league average 100%. Tango’s more sophisticated methodology indicates that his true talent should regress to league average by 1-(# of FB/(# of FB+627)). Since Cain has given up 1415  fly balls, we should expect him to regress about 30% towards the league average of 0.106 HR/FB. That would mean that Cain’s true talent is about 0.78. That means that if he were to give up a similar number of flies this this year, we could expect about 1.5 more home runs. That’s kind of not a big deal.

Now that all might change if he switches ballparks. I am still not clear about AT&T park’s role in this. As Paapfly points out, Cain actually has a lower HR/FB on the road, so whatever AT&T’s effect is, it can’t be the dominant one. That odd split is probably explainable by luck influencing a smaller sample of road flies. However, the Giants in general seem to do oddly well on the road. Since 2005 all Giants pitchers have combined have the best HR/FB at home, and  also the best HR/FB on the road!

It’s also worth noting that while all the debate focuses on Cain’s HR/FB magic, that’s only a part of Cain’s overall weirdness.There are 120 pitchers that have thrown at least 500 IP, since Cain’s debut. Of those, Cain ranks 5th in BABIP (.266) and tied for 15th in strand rate (75.2%). A pitcher’s strand rate  is clearly more a luck influenced stat than a luck driven stat, but Cain’s is still higher than you would expect given his peripherals.

There’s still a few questions left to answer about Cain’s extended run of statistical freakishness. I would like to know just how sticky his infield-fly rate is from season to season, when compared to the average pitcher, and how well that correlates with weak contact to the outfield. I want to know whether that’s the reason for his exceptional strand rate. Lastly, I’d like to know if the Giants recent run of exceptional OF defense is partially responsible for Cain’s low BABIP, or whether Cain is making the outfielders look good through weak contact.

I am personally delighted this debate his erupted into the general baseball arena.  Giants blogs can take a crack at all of these questions, but there can be no denying that the urge to confirm the awesomeness of our favorite players is strong. The Giants-aligned stat blogs have done a great job challenging the conventional wisdom, but knowing that Dave Cameron or Tom Tango might try to rip apart your argument is bound to keep the quality of those arguments higher.

**UPDATE**

Apparently Dave Cameron is as fascinated by Matt Cain as I am. He notices a pattern amongst Giant pitchers over the decade, and wonders if maybe Dave Righetti possess some arcane knowledge about keeping the ball in the yard. (thanks to marcello for the tip).