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Originally Posted by old timer
I just did some tests where I tweaked the A's and Dodgers defensive ratings for a few of their players that I thought were off and both teams BABIP and overall performances were similar to real life. This happened in multiple tests. Without these adjustments, both teams BABIP were much higher than in real life and both generally performed far worse too.
In other words, defensive ratings do seem to be a big problem, but how to fix? Does anyone aside from Markus even know how the ratings are calculated upon importing?
If we had direct access to the game database, we could make a utility that could modify the ratings based on our own algorithm. I don't think he's going to give us such access, however. So short of asking Markus to improve his algorithm and hoping he looks at it, is there anything practical that we can do that would help him improve the defensive ratings?
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First things first. My suggestion would be to see if an accurate "season disk" can be created for 1974 that would touch nothing but defensive ratings, and would do that objectively, using the metrics on baseball reference, or fielding win shares, or other available advanced stats. If it could be done for that season, then the methods could be generally applied to other seasons for which those advanced stats were available.
It's also possible that the way to go, which would be doable within the Lahman database, is to develop a "team defense" metric, within which all of the defensive ratings would be modified by a set percentage according to team runs allowed. Or, if you've read the Bill James book on Win Shares, you'll remember his efforts to break those down between pitching and fielding. He has multiple formulae that he used to do that. Rather than reinventing the wheel, I suspect we could find a place on the net that broke those down for every team in baseball history. We could correlate those with the existing defensive ratings. I'm open to suggestions from interested parties. As I said, the first test would be to see whether we could use objective criteria to get 1974 right.