Those money-grubbing sabermetricians are at it again! Furthering their journey down that money trail, talented Baseball Prospectus writers Matt Swartz and Eric Seidman unveiled a new pitching statistic, "Skill Interactive Earned Run Average" (SIERA, for short). It is rooted in the DIPS concept, like FIP and tRA, and was explained in a series of posts this past week:
The formula for the new stat should instantly convert flat-earthers to saber-lovers:
SIERA = 6.262 – 18.055*(SO/PA) + 11.292*(BB/PA) – 1.721*((GB-FB-PU)/PA) +10.169*((SO/PA)^2) – 7.069*(((GB-FB-PU)/PA)^2) + 9.561*(SO/PA)*((GB-FB-PU)/PA) – 4.027*(BB/PA)*((GB-FB-PU)/PA)
Ouch. Commence blog posts longing for simpler times when a math degree wasn't necessary to enjoy the crack of the bat, smell of the grass and taste of a cold beer at the old ballpark.
In all seriousness, this seems like a useful new stat to use side-by-side with FIP and the like, but who knows. I'll let people smarter than I examine it, offer criticisms and determine how much value it adds to what is already available. That's one of the great aspects of the sabermetric community -- when something new is introduced, there's a lineup of usual suspects ready to frisk it. If the new stat is bogus, it will be exposed and forgotten.
Swartz and Seidman nicely outlined what SIERA should accomplish in their Part 1 piece -- click through to check them all out. Here is a preview, in which they used Johan Santana as an illustration for one of the SIERA attributes:
2. Allows for the fact that a low fly-ball rate (and therefore, a low HR rate) is less useful to pitchers who strike out a lot of batters (e.g. Johan Santana's FIP tends to be higher than his ERA because the former treats all HR the same, even though Santana’s skill set portends his bombs allowed will usually be solo shots).
Johan's ERA has historically outperformed DIPS and perhaps this is a reason why. For more on Santana, check out Part 5.
Courtesy of the SIERA calculator at Braves blog Capitol Avenue Club (BP hasn't yet put up SIERA leaderboards), here are the 2009 SIERA's for potential 2010 Mets pitchers, minimum 50 big league innings. Various other stats are also listed:
Looks like we found Ollie's new favorite stat.