"I have not failed. I've just found 10,000 ways that won't work."
--Thomas A. Edison
We learn as much or more from our failures as we do from our successes; a lesson Edison learned in spades as he worked to develop the incandescent light bulb. Of course, he was also the holder of 1,093 patents, so he certainly enjoyed his successes as well. And while our little dabblings in baseball analysis in no way compare to the work of true inventors, we do share the common experience of sometimes having to engage in significant rework of an idea to bring it just a little closer to where we want it. So this week we revisit the topic of outfield defense and take a slightly different perspective in creating a play by play fielding metric for outfielders. We've already got version 1.0 of SFR for infielders, which was discussed last week.
However, before we delve back into the topic of outfield defense, I want to make good on my promise to release some minor league numbers. So at this link you'll find the same spreadsheet linked to in last week's article, this time with a new tab that includes all 10,774 2007 minor league player, team, and position combinations. Have fun.
We now return to our regularly scheduled topic.
A Different Approach
After my last foray into outfield defense a few weeks ago I received helpful feedback from readers and the sabermetric community at large in relation to the methodology I employed to calculate the SFR values. For those who weren't with us last time, we can describe the algorithm described in that column like so:
- First, calculate a baseline for the year and league that includes the percentage of balls that fall for hits and the resulting total bases across the following axes: position, hit type (fly, line drive, pop up, and ground ball), and batter handedness. The resulting matrix will be used for comparison purposes.
- Calculate the same matrix for each fielder for the year and league in question and compare the matrix to the baseline in order to calculate the expected number of runners and expected total bases given the same number and quality of opportunities. Each difference in the number of expected runners is credited at 0.74 runs (0.46 for the hit plus the negative of -0.27 for the out) and each additional total base above and beyond the number of expected runners is credited at 0.33 runs (the difference between the value of a double and a single).
- Because outfielders are much more constrained by their park than infielders are, we need to make a park adjustment. This is done by creating a three-year park factor for each park and position using the same context (hit type and batter handedness) as above. The park factor is calculated by comparing all plays at the park and position in question with all plays in games by the home team when on the road. In other words, the park factor is calculated as the ratio of the rate at which balls are turned into outs and extra bases are gained at home, versus that done on the road over a three-year span. The park factor (not weighted but simply averaged over the three years) is then applied to each fielder opportunity at each park with the result being the adjusted SFR value.
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