UZR seems to suggest that such an outcome is reasonable. Hanley Ramirez was terrible defensively last year in LF and had a -30 UZR/150. Manny Ramirez had a few years where he had a -30 UZR/150 in LF. Unlike these players, Wieters has no experience playing in a corner outfield position and could very possibly struggle to make even simple defensive plays. If the worst corner outfielders are worth -30 runs, then Wieters could be worth -50 runs.
On the other hand, there are a limited number of balls hit to corner outfielders in a game and most of them are either easy or impossible plays. According to Inside Edge Data, only 40 to 50 balls hit at corner outfielders per season are even in question. A defensive outfielder would need to consistently botch the easiest plays that require minimal range to be worth 50 runs below average. Even a slow professional baseball player would be challenged to perform that poorly.
Furthermore, Machado is an excellent fielder and is only about 10 runs above average defensively at third base. Simmons is an excellent shortstop and is usually 20 runs above average defensively. If UZR values the worst corner outfielders as worth -30 runs defensively, does this mean that there's a problem with UZR? It seems difficult to see how an experienced corner outfielder could cost his team that many runs.
Fangraphs argues that WAR works because there is a strong correlation between a team’s total WAR and their actual record. Glenn Dupaul from the Hardball Times argues that if WAR does a correct job at explaining where wins come from, the linear regression equation should have an intercept equal to roughly replacement level (47.7 wins) while each WAR should be worth roughly one win.
When I did this test with data from 2002-2015, the resulting formula returned had an intercept of 47.6 wins with each WAR being worth 1.00093 wins. When I split WAR into pitching and position WAR, the resulting formula was 46.84+.89*Position WAR+1.20*Pitching WAR which has interesting implications when thinking about this article. In any event, there can no debate about whether WAR works even if it could potentially be improved.
This is relevant because UZR is part of the WAR formula. One way to determine whether UZR works is by breaking WAR up into its components and seeing whether UZR is a significant factor for predicting teams’ total wins. I did such a test using a stepwise regression and found that it is significant. It was the third most important factor behind pitching and hitting although considerably less important than either of the other two. This implies that UZRs’ efficacy is limited, but still better than nothing.
The next question is whether UZR works for each position and specifically LF or RF. For this test, I input each teams’ defense score at each position (in order to replicate this it’s necessary to grab the data from the Fielding Tab rather than the Batting Tab at Fangraphs) for each team and season. For most positions, UZR is helpful. Surprisingly, first base defense seems to have the highest correlation with wins (which possibly implies something about how defense is measured at other positions), while third base and center field data are also helpful. Data from shortstops, catchers, left fielders and right fielders are less helpful but still add some certainty. Surprisingly, second base defense as measured by UZR doesn’t add predictive power to the model.
The last question is which aspects of UZR are relevant for each position. Just because one aspect of UZR is relevant for a given position doesn’t mean that all of the aspects are relevant. In order to test this, I used each teams’ range, error, arm and double play range for each position to see which ones can be used to model wins. None of these factors apply to catchers and therefore this method can’t measure their performance.
My results suggested that range is relevant for first basemen, third basemen, center fielders, shortstops, extremely minimally for second basemen and has no relevance for corner outfielders. This is problematic because range is the largest component to UZR and therefore suggests that defense values for three positions are valued improperly and in a format that doesn't help us predict team wins.
Likewise, errors are only relevant for third basemen and shortstops. The average team’s left fielders have 5.2 errors over a season. The 75th percentile is 7 errors while the 25th percentile is 3 errors. Right fielders average 5.75 errors over an entire season with the 75th percentile having 7 errors and the 25th percentile having 4 errors. Even if an outfield error costs a team .8 runs, that still means errors from left fielders cost most teams about three runs a season and about two runs for right fielders. Similar stories can be told for center fielders (average=4.8, 75th percentile = 6, 25th percentile = 3), first base (average = 10, 75th percentile = 13, 25th percentile = 7) and second base (average = 13, 75th percentile = 16, 25th percentile = 10).
The only statistic that is relevant for corner outfielders is arm strength. This would work for a player like Wieters as he’d likely struggle with range and errors but has a strong arm. It also means that teams are right if they discount UZR range values for corner outfielders and players like Heyward could be overvalued due to possibly overvalued defensive ratings.
The bottom line is that it is hard for us to accurately measure corner outfield defense and therefore can't determine how much damage a bad defensive outfielder inflicts on his team.