SoSH Glossary: Zone Rating

Baseball is filled with statistics, rules, and archaic terms that can often form what sounds like a foreign language.The Sons of Sam Horn glossary provides a better understanding of these terms through straightforward definitions, clear explanations, and examples pulled straight from the baseball world. If there is anything you would like us to add to our glossary, please contact us.

Zone Rating, now referred to Revised Zone Rating (RZR), measures the percentage of balls in play in a fielder’s area of responsibility that he registers as an out. The statistic seeks to measure a player’s range and was created by John Dewan in the late 1980s. Dewan would later make adjustments to zone rating in the early 2000s which is why it is now called RZR. The field is divided into 78 zones, and if a position is responsible for at least 50% of the outs recorded in a given zone then that position is responsible for that zone. In its current form, RZR measures four things:

  1. Balls in play within a player’s zone (BIZ)
  2. Outs made in a player’s zone (PLAYS)
  3. Percentage of plays made in a player’s zone (RZR)
  4. Total plays made outside a player’s zone (OOZ)

Bunts and pop flies are excluded from the calculations, and balls must travel at least 69 feet and 59 feet to be counted for middle infielders and corner infielders, respectively. Double plays count as one out, which is one of the major adjustments Dewan made in the 2000s.

Only balls in the air, line drives and fly balls, are counted for outfielders. The only foul territory that is considered are the areas near the first and third base bags for ground balls that are ruled fair.

The league-average RZR is usually around .825. OOZ is simply a counting stat, and is the other major change that Dewan made in the 2000s as OOZ were formerly counted within RZR.

Limitations

Zone rating depends on those collecting the data to properly classify the zones in which balls are hit. Two different evaluators could believe that the same ball was in two different zones on the same play. RZR does not take into account how hard balls are hit, nor where in the zone the ball is hit. This means that it treats all balls within a given zone as equal, which is not true. Some hits will be much more difficult to field in the same zone compared to others.  RZR also does not take defensive shifts into account, which fundamentally alter the areas of responsibility for the fielder, at least on a play-by-play basis, adding a layer of complexity to the subjective limitations listed above.


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Pete is the Editor-in-Chief of Sons of Sam Horn. Currently residing in North Carolina, he enjoys reading and spending time outdoors when not editing or working with his tremendous team.

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