This year all outfielders will receive an optional “lf/rf” rating. This is a combined rating based on all OF defensive range data. It is recommended that you use the combined rating as it is a more accurate representation of the player’s overall defensive performance. The individual position ratings are based on smaller data samples and frequently result in widely divergent ratings (e.g. a “G” rating in LF and a “K” rating in RF).
Before a combined rating could be created it was necessary to determine conversion rates, e.g. how does range in LF translate to range in RF. I collected the unadjusted (raw rating before playing time adjustments) range ratings for all outfielders from the last four years and calculated each player’s positional range differentials (e.g. lf-rf). An overall differential for the entire pool was then calculated by weighting each player differential by the lowest amount of innings played at either position.
Example: In 2013, Roger Bernadina had an unadjusted range of 0.656 (0.0 = K, 0.5 = F, 1.0 = A) in 146 LF innings, 0.352 in 139 CF innings, and 0.550 in 223 RF innings. This resulted in a lf-rf differential of 0.106 weighted by 146, a cf-lf differential of -0.304 weighted by 139, and a cf-rf differential of -0.198 weighted by 139.
Data for each year:
. lf-rf cf-lf cf-rf cf-of
2014 0.026 -0.129 -0.241 -0.165
2013 -0.012 -0.161 -0.146 -0.161
2012 -0.005 -0.152 -0.175 -0.182
2011 0.030 -0.159 -0.187 -0.179
It became clear that there is no functional difference in LF/RF range, so for the CF conversion rate I decided to calculate the differential between CF range and combined LF/RF range (“cf-of”).
As a result of this data analysis, the combined LF/RF range treats LF and RF range equally and a bonus of 0.175 is applied to CF range. In the case of Bernadina, his raw combined LF/RF range is:
(0.656 * 146 + (0.352 + 0.175) * 139 + 0.550 * 223) / (146 + 139 + 223) = 0.574
Standard rules are then applied for playing time adjustments. Since we are using aggregated data there is no need for a complicated bonus system.