Defensive metrics disagree on the 2017 Detroit Tigers

Advanced metrics continue to grow in baseball as technologies become more and more sophisticated. However, as batted ball and pitch movement data grows, measuring defensive ability is still proving to be a challenge. Sabermetricians have improved at calculating fielder positioning and movement as well as metrics such as catch probability, but declaring any statistic as a definitive is not possible at this time.

As of right now, the two best ways to calculate defensive value are Defensive Runs Saved (DRS) and Ultimate Zone Rating (UZR). These two metrics both attempt to capture fielding ability by using a variety of inputs and assigning an arbitrary score to each player, and subsequently each team. While it is difficult to place one significantly ahead of the other, in combination they often give a reasonable estimate of a player or team’s defensive value.

Of course, sometimes DRS and UZR do not agree. The 2017 Tigers are a great example of this potential discrepancy. With -60 DRS, the Tigers rank second to last in baseball this season, ahead of only the New York Mets. Meanwhile, Detroit’s 4.6 UZR actually ranks them in the top half of the league. Only the Brewers show a bigger rankings gap than the Tigers; conversely, Milwaukee has a much higher DRS than UZR.

This gap is uncommon, and especially for the Tigers. Over the past five seasons, DRS and UZR have been on the same page when grading Detroit’s ability in the field. When the Tigers were good — basically just one season — they ranked in the top 10 in both metrics. When they were bad — every other year — their rankings sat near the bottom in both stats.

What happened in 2017 then? The answer lies in the calculations of the metrics. At a high level, DRS and UZR look at many of the same criteria. While UZR has a slightly longer historical comparison window, the stats are generally attempting to accomplish the same goal, which is to calculate a player’s value based on their defensive success rate.

DRS looks at six factors: stolen bases for catchers and pitchers, bunts for corner infielders, double plays for middle infielders, advancing runners and home run robberies for outfielders, and range. The Tigers rank favorably in just one of these: they sit 10th in double play creation. Every other component finds Detroit ranked 20th or worse, and it is hard to argue against any of these stats with the eye test.

UZR also looks at double plays for middle infielders, advancing runners for outfielders, and range, but additionally takes into account errors. While the Tigers rank poorly in outfielders limiting advancing base runners and overall range, they ranked sixth in the double play component and second-best in minimizing errors.

The Tigers have the sixth-fewest errors and seventh-highest fielding percentage in 2017, so their higher UZR, a metric which includes error prevention and puts a higher weight on middle infielders, should not be surprising. The individual components of the two metrics were fairly similar; it is just their difference in emphasis that really separates DRS and UZR for the Tigers.

A higher UZR may be a false representative for the Tigers, too. While limiting errors is important, the reason why advanced metrics are so valuable is that they factor in more than just traditional fielding percentage. With below average numbers in almost every area outside of double play turning, the Tigers do not have much to be proud of. 2017 was yet another year of mediocre fielding in Detroit.