, range factor, or RF
, is one of the best available statistics to measure a fielder
's defensive prowess. To find a player's range factor over a given time period, first add putouts
and then divide by total innings
played in the field, like so:
(PO + A)
The idea behind range factor is actually quite rudimentary: it simply measures the number of outs a fielder is involved in. But when measured over a long enough period of time, say for example a season, the player with the higher range factor is almost invariable the better defensive fielder. Not surprisingly players like Andruw Jones and Alex Rodriguez consistently have high range factors, and Ozzie Smith has the highest career range factor of any shortstop in baseball history.
Range factor is vastly superior to fielding percentage, the more traditional measure of defensive value, because fielding percentage is based entirely on errors, which often have more to do with a player's luck than his skill or lack thereof. Range factor is particularly useful in comparing players across eras and on different playing surfaces, and has the additional benefit of being easy to calculate (especially when compared to other modern defensive stats, such as zone factor). Range factor's main deficiencies as a stat are that it usually only be used to compare players fielding the same position, and that it is not very useful when anayzing short periods of time, when a player's number of fielding chances can be skewed by luck.