Decoding UZR

What is behind the Ultimate Zone Rating and its use in evaluating baseball players’ defense?

UZR, which stands for Ultimate Zone Rating, is a statistic used in baseball to measure a player’s defensive ability. It is used to assign a numerical value to a player’s defensive performance based on how many runs they are estimated to have saved or given up compared to the average player at their position, but it does have some stark differences from Defensive Runs Saved (DRS).

UZR is calculated using a combination of play-by-play data, pitch tracking data, and other information to estimate the number of runs that a player has saved or given up due to their defensive abilities…or lack thereof. The statistic considers several factors such as range, arm strength, and positioning. It also takes into account the specific context of each play, such as the type of pitch thrown, the count, and if the hitter is batting lefty or righty.

One important aspect of UZR calculation is assigning run value to plays. A UZR calculation assigns a run value to each ball put in play based on where it is hit, whether it is a line drive or a fly ball and whether it is hit with a man on base. These values are used to estimate the number of runs that the player saved or gave up relative to an average player at their position, which is the main difference between DRS and UZR.

UZR also uses a multi-year regression analysis on the player. It analyzes a large sample of plays over multiple seasons to determine the defensive performance of the player relative to others at their position. It also adjusts for park effects and league averages in order to produce a more accurate measurement.

It is important to note that UZR is an estimating statistic, it’s not meant to provide a precise measurement of a player’s defensive abilities, and like all statistics, it has its limitations. It is also important to use UZR in conjunction with other defensive metrics, like DRS (Defensive Runs Saved) and Good Fielding Plays/Misplays (GFP/GPM) to get a more comprehensive picture of a player’s defensive abilities.