At the SABR Analytics Conference in Phoenix, SABR announced that it would team up with Rawlings in order to: 1) create a new fielding metric called SABR Defensive Index (SDI) and 2) use SDI as one contributing factor to determine the Gold Glove Award.
Last week, SABR announced more details about the project. Here's the significant excerpt from the press release:
Gennaro said a high priority for the new Fielding Research Committee would be to establish a transparent index that integrates respected fielding metrics from multiple sources.
"The baseball community's knowledge of defense, and the data we use to evaluate it, is improving every day," Gennaro said. "In keeping with SABR's mission, and the goal of the Analytics Conference, we hope the SDI will be an ongoing effort to integrate the best research and the best methods available to assess defensive performance."
The key points we can draw from this are the following:
- SDI will integrate various advanced fielding metrics (presumably metrics like UZR, DRS, and FRAA)
- SDI is an index, meaning it will normalize the metrics so that they are on the same scale and can be compared and integrated as such.
- SDI will be transparent -- that is, hopefully, the formula and calculations will be open to the public.
SDI will incorrectly be viewed as sabermetric progress
Settling for a sub-optimal defensive metric will make it difficult to improve the Gold Glove going forward
There is no need to combine all the metrics into one number
Sure, UZR and DRS and FRAA are all flawed in one way or another, and sure, using them in the Gold Glove is not the ideal answer. Nevertheless, there is clearly no analytical benefit to combining them all together other than for the sake of simplicity. The Gold Glove can still include these metrics without creating The One Number that will say everything about a player's defense.
If, instead, SABR simply provided a guide that included the metrics -- as they said they would do -- but did not create an all-encompassing metric, there would be less risk of misunderstanding and more room for progress. By separating these metrics, the implication is that none are the perfect answer, and that they each give us a different answer. Voters and fans can then use the metrics as they see fit, but will have a clear understanding that no individual number says everything about a player's defense.
I fully understand the concerns coming from many members of the sabermetric community regarding the SABR Defensive Index, especially those who were already skeptical of defensive metrics to begin with. Nevertheless, though SDI is certainly not progress within the sabermetric community, it would likely improve the accuracy of the Gold Glove Award.
The issue with SDI lies in its potential to confuse fans and voters, damage the credibility of sabermetrics, and slow real progress in measuring defense. However, I believe that these concerns mainly lie in the fact that SDI combines the defensive metrics available, rather than leaving each one as publicly available and independent of one another.
If we can all agree that both the Gold Glove methodology and advanced defensive metrics need to be improved, we, as a sabermetric community, should worry less about SDI and more about educating the public about the pros and cons of defensive metrics available and working towards more accurate, understandable, and transparent methods of evaluating defense.