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Monday, March 22, 2010
Batted Ball FIP chart
Rich is so close to representing Batted Ball FIP as a chart. He took the necessary first step as doing K minus BB. But, he keeps GB/BIP as the other term. By doing GB/BIP, it’s the exact same thing as doing (1-GB)/BIP. And 1-GB is outfield FB plus infield FB plus line drive.
As we know from MGL’s DIPS Primer from several years back, and reiterated with SIERA recently, the frequency of line drives is not very persistent pitcher-to-pitcher (in MLB). The reason should be clear: if you give up alot of line drives, you will be weeded out of MLB! Basically, you and me won’t make it to MLB, because at least 50% of the batted balls would be line drives. 85% of MLB pitchers give up line drives at the 18%-22% level in their careers. Even the pitcher with the most line-drive preventing skill (Derek Lowe) gives up 16% line drives, and he’s only that low because of his excessively high GB rate. That is, the low correlation is not an indication of a lack of skill, but an indication that at the MLB level, there is not much variation in that skill.
What can Rich do? Well, he can do what Batted Ball FIP does, and make it GB-ofFB per BIP. What this does is distribute the line drives and infield flies evenly to GB and FB. For example, say you have this:
GB: 40%
ofFB: 30%
LD: 20%
ifFB: 10%
This will give you the same thing as:
GB: 45%
ofFB: 35%
LD: 10%
ifFB: 10%
That is, the GB minus ofFB is 10% in either case. It’s an acceptance that the line drive doesn’t affect either one. Now, the only question is if you should do GB minus ofFB or GB minus ofFB+ifFB. There is a high correlation between ofFB + ifFB. So, SIERA takes the position that you should simply lump them into FB. At the same time, there is a huge run difference between an ofFB (about +.05 runs) and an ifFB (about -.30 runs) that it would be understandable to keep them separate, as I (currently) do. I still haven’t decided whether to keep them together or not, though currently, I’m keeping them separate.
So, to Rich, I recommend that you do GB minus FB, and you can decide whether FB includes or excludes pop ups.
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