Thanks to the wonderful book The Last Nine Innings by Charles Euchner1It details the stunning victory of the Arizona Diamondbacks over the New York Yankees in the 2001 World Series. I had an early introduction to some advanced statistics, at least those that were popular a few years into the 21st century. Among these was Ultimate Zone Rating, a first crack at trying to measure how well a player defends their position.
In short, Ultimate Zone Rating is a tool to convert defensive ability into runs saved (or allowed). We look at how frequently a particular batted ball is converted into an out, how many runs such a ball would be worth on average, and thus determine how many runs saved that play is worth if it is made.
As noted yesterday, defense is messy. The detailed FanGraphs UZR “Primer” (quotations are mine) is sixteen parts. There are a few reasons for this.
- Gathering and categorizing the data is difficult.
- Every defensive position has a unique role, so attempting to quantify each position and account for their differences2For example, the strength of an outfielder’s arms is very important, as compared to the second baseman’s. We need to account for that. Another example is that double plays are very important, but mostly happen with infielders. makes things complicated.
- Infield positioning choices, largely decided by team management, affects how likely a player is to get to a batted ball.
But, UZR is understandable at a high level. It has four components, not all of which are relevant for everyone.
- Range Runs – This measures a player’s ability to get to a ball in play compared to an average player at their position.
- Error Runs – This measures how frequently a player makes an error compared to average.
- Outfield Arm Runs – This accounts for an outfielder’s effect on the game: a strong arm can prevent a runner from advancing to the next base.
- Double-Play Runs – Infielders can be adept at turning double plays in key situations.
With those caveats and outline, let’s talk a bit more about using UZR. It’s similar to other run-accumulation statistics we’ve seen, where 0 is average for their position. A player’s UZR can then be positive or negative based on how many runs they’ve saved (or allowed) over time. Since defensive performance can be variable in the same way that certain batting statistics (like BABIP) can be, looking at trends over several years is the best approach.
Let’s put that into practice.
A Comparison
In 2015, Nolan Arenado had a UZR of 4.1, while Trevor Plouffe’s was 3.4. That’s pretty close! But, we don’t want to look at a single season to compare overall defensive ability. Let’s look at the prior two seasons as well.3After 2015, Plouffe played far fewer innings at third, so his UZR would naturally be lower. Although, it’s worth noting that in 2016 he played less than half his 2015 innings at third, during which his UZR was -5.7. Ouch.
In 2013 – 2015, Arenado’s UZR was 14.6, 3.1, and 4.1. Clearly he had some major regression after his rookie year in 2013, but he still accumulated 21.8 runs saved during that time. Plouffe’s values were -2.8, 5.1, and 3.4, for a total of 5.7 across those three years.
We could also look at seasons during which they were the same age. Since 2013 through 2015 were Plouffe’s peak years of consistent playtime, when he was age 27 through 29, we’ll compare that to 2018 through 2020 for Nolan Arenado, while noting that 2020 was a shortened season which may affect an accumulation statistic like UZR.
We already have Plouffe’s values from above; Arenado’s UZR during his age 27 through 29 seasons were 5.8, 10.3, and 8.5.4Note that even during a shortened season, less than half the length of a regular season, he saved 8.5 runs (above average). That’s ridiculous. That’s a total of 24.6 runs saved, over 4 times as many as Plouffe.
Continue to Day 23 – Defensive Runs Saved and Defensive WAR
- 1It details the stunning victory of the Arizona Diamondbacks over the New York Yankees in the 2001 World Series.
- 2For example, the strength of an outfielder’s arms is very important, as compared to the second baseman’s. We need to account for that. Another example is that double plays are very important, but mostly happen with infielders.
- 3After 2015, Plouffe played far fewer innings at third, so his UZR would naturally be lower. Although, it’s worth noting that in 2016 he played less than half his 2015 innings at third, during which his UZR was -5.7. Ouch.
- 4Note that even during a shortened season, less than half the length of a regular season, he saved 8.5 runs (above average). That’s ridiculous.