For the 2017 season, Mitchel Lichtman has made some improvements to the UZR methodology!
– UZR now uses hit timer data (hang time) rather than hit type designations, which is an improvement on the methodology and thus the results.
– The methodology has changed a little that allows UZR to account for some of the noise associated with imperfect data. The net result of this change is that extreme UZR’s, which were likely caused by, to some extent at least, noise in the data, rather than extreme performance, will be slightly ‘dampened.’ We think that these new values, while very close to the old ones in most cases, more accurately reflect the actual performance of the players in question.
These changes in UZR are currently active for 2017, and will also be rolled out for 2012 – 2016 data in the near future.
David Appelman is the creator of FanGraphs.