## Where DRS and UZR disagree

Kelvin Kuo-USA TODAY Sports

We usually like to have confirmation from multiple sources about the statistical measurements of defense. Where might two main sources disagree?

Defensive statistics are still coming along. To evaluate a single player, a rule of thumb is that we need three seasons of defensive data to make accurate assessments of defensive ability. On a team level, less time is needed. There are two main systems for defensive statistics housed on FanGraphs. Defensive Runs Saved, or DRS, and Ultimate Zone Rating, or UZR. DRS is calculated by John Dewan's organization, The Fielding Bible. UZR was created by Mitchel Lichtman. In both systems, a value of zero is considered average for the position; anything above zero is above average and anything below zero is below average. You can read the explanations for each system at the FanGraphs glossary (DRS here and UZR here).

On a team level, there are actually several teams whose DRS and UZR numbers disagree. Before presenting the teams, I took some liberties with how I defined "disagreement". First, I looked for those teams whose UZR and DRS numbers had opposite signs (positive for one number and negative for the other). This gave me a list of teams that one system determined as above average while the other determined as below average. I then sorted by the absolute value of the difference between the two systems. Here are the top 5 teams with their corresponding DRS and UZR numbers (numbers as of Sunday).

Team Inn DRS UZR
Pirates 5544 25 -21.2
Nationals 5427 7 -18.7
Angels 5502 -2 23.5
Mariners 5442 -12 11.2
Dodgers 5697 5 -16.3

It would appear that the Pirates are confusing the systems. DRS sees them as a very good defensive team, while UZR sees them as a very poor defensive team, and the difference between their numbers is almost twice as large as any other team's difference. The Nationals, Angels, Mariners, and Dodgers all have about the same degree of difference between the two numbers.

What are we to make of these numbers? How do we know which is right? There are a few indicators we could peruse: BABIP, LOB%, and ERA-FIP. The idea is that teams with better defenses will have lower BABIPs, higher LOB% numbers, and an ERA that beats their FIP. Here are those same five teams with those statistics.

Team BABIP LOB% ERA FIP E-F
Pirates 0.284 73.3% 3.83 4.06 -0.23
Nationals 0.300 74.7% 3.00 3.15 -0.15
Angels 0.280 72.0% 3.84 3.79 0.05
Mariners 0.277 75.7% 3.41 3.78 -0.37
Dodgers 0.299 76.1% 3.41 3.71 -0.30

The Pirates, Angels, and Mariners all have below average BABIPs. The Pirates and Angels have relatively pitcher-friendly ballparks, but they also have Andrew McCutchen, whom the numbers don't like, and Mike Trout, who by the numbers is just okay. The Nationals, Mariners, and Dodgers each have a LOB% above average, and the Dodgers have Yasiel Puig. Only the Angels do not have a team ERA below their FIP.

Based on this, there is some evidence that these teams are decent defensive teams, but it's difficult to disentangle the effects of pitchers, ballparks, and defense on BABIP, LOB%, and ERA-FIP. Like with many things in baseball, and in life, the answer of whether these teams are good defenders or bad defenders is probably somewhere in between, or perhaps the evidence for either side will show itself as the season continues.

. . .

All statistics courtesy of FanGraphs.

Kevin Ruprecht is a Featured Writer for Beyond the Box Score. He also writes for Royals Review. You can follow him on Twitter at @KevinRuprecht.

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