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I do the annual defense updates, um, annually. That’s once a year. It’s a fairly complicated process which means each year when I come back to do the task I’ve forgotten some of what I was thinking the previous year. I don’t think I’ve done it precisely the same in any two years in a row, although I don’t know for sure.

Last year was in some ways the worst. The details are complicated and I’m not sure I can reproduce all of them in any case, but the upshot was I had a few cases where a player had not played at a position the previous two seasons but still enjoyed a nice rating from before that. I don’t remember who was affected, but there was someone who had gotten good ratings in 2011 for a few innings in the OF and carried that good rating into play in 2014, despite having been banned from the OF for the intervening years because he really was sort of klutz.

I used the old data to try to make our ratings more predictive of performance in 2014. Fielding is hard to measure, and the best measurements are pretty volatile. SO the best practice when forecasting future performance is to get as big a sample as possible. So starting several years ago, to calculate opening day ratings, I weight the previous year with a factor of 3, the year before that at 2, and the year before that at 1.

This is great for players who played the whole time. And it allows us to consider all their playing time, to avoid being too skewed by small samples. But if, like last year, I end up just carrying forward a few 3-year-old innings, you can get a crazy result.

The rules only mention using the previous year’s data. But this is unfair to a sterling defender who misses a year for injury. So I have not considered that comment binding. The rule mostly gives highly general instructions and then leaves the details to the commissioner.

This year I have rigged it up to try to take advantage of three years’ data when it exists, without leaving us exposed to using old data if the player has goe two seasons without playing at a position. My spreadsheet uses all three years only if one of the two most recent years also includes defensive stats at a position.

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So player A has played in 2012, 2013, and 2014 at 3d base. I count all his innings, weighting 2013 twice as much as 2012, and 2014 three times as much.

Player B played 3b in 2012 and 2014. I count all his innings, weighing 2014 three times a much as 2012.

Player C played 3b in 2012 and 2013. I count all his innings, weighing 2013 twice as much as 2012.

Played D played 3b in 2012, but not since. He’s taken two years off from the position. It’s unusual to come back to a position after two years off, but it has been been done. Chone Figgins going back to second for the M’s comes to mind. However, this player will not have a 3b rating to start 2015. If he picks up his 3d base glove again in 2015, he’ll start over at a replacement rating.

Does this sound fair?

Does it even matter?

Should I start following the narrowest interpretation of the rule? Or do something else?

Below is the rule. And below that is the list of catcher ratings for opening day 2015, using my new approach where two years away from a position means you start over (ed. note: catcher ratings actually appear here).

RULE: For the 2010 season, the Commissioner will determine opening day defensive ratings by averaging APBA ratings for 2009 and a selection of at least three defensive metrics that determine a playerâ€™s value in terms of runs allowed or games won/lost. For seasons beginning in 2011, the APBA ratings will be dropped from these calculations. As the season progresses, the Commissioner will periodically update defense ratings by using metrics of the playersâ€™ performance during the season. If a player has no defensive rating from the previous year at a position, he receives the replacement rating at his first appearance at that position, as follows: C: 6.0; 1b: 2.0; 2b: 6.0; ss: 7.0; 3b: 3.0; of: 1.0. A player with no defensive ratings at all receives a replacement rating at the position the Commissioner determines is his main defensive position.

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