On Sunday, the Pirates announced their plan to reconfigure their defensive outfield in 2017, moving long-time center fielder Andrew McCutchen to right field, Gregory Polanco to left field, and defensive stalwart Starling Marte to center field. Based simply on their Defensive Runs Saved (DRS) totals from 2016, the move makes sense. Marte led all left fielders with 19 Runs Saved despite missing most of the final month with a lower back injury, so he seems like one of the best corner outfield candidates to move to center. Meanwhile, McCutchen has seen his defensive numbers decline in center for several seasons now, culminating in a -28 DRS total last season that was the worst of any player at any position.

However, this realignment is more difficult to evaluate than it appears at the surface. That is because, not only are there different numbers of opportunities for the different outfield positions, the defensive quality of an average player at each outfield position is different. Marte is undoubtedly a good defender, but DRS is calculated relative to the average player at a given position. Therefore, one reason his DRS totals are as high as they are is because some teams opt to play sluggers with poor defensive skills in left field, which weighs down the average fielder there and makes Marte look even better by comparison. In contrast, most teams deploy their best defensive outfielder in center field, so McCutchen would likely look better in comparison to the lower standards in the corner outfield.

To make sense of it all, we’ve found every player who played at least 300 innings in one outfield position one year and then 300 innings at another outfield position the next year, and we’ve calculated a weighted average of the change in their Defensive Runs Saved per 100 opportunities from one year to the next. For these purposes, an opportunity represents any flyball that a fielder at a given position had a chance to catch, which is based on our Range and Positioning system.

As one would expect, the move from center field to right field produces the biggest gain in Runs Saved, and so McCutchen should expect a significant improvement to his DRS total at his new position. However, based on previous examples, left fielders who have moved to center field have lost more runs per 100 opportunities than center fielders who moved to right field have gained, -3.8 to +3.2. Given that the move from right field to left field has been close to neutral (+0.3), does that mean the Pirates might actually make things worse with their realignment?

The answer is no. Even with the expected decline for Marte and expected gain for McCutchen, they are projected to remain above and below average defenders, respectively. Meanwhile, the new alignment should mean their above average fielder, Marte, has more opportunities to make plays while their below average fielder, McCutchen, has fewer opportunities.

In 2016, an average outfield saw 530 opportunities in center field compared to just 448 in right field and 410 in left field. If you pro-rate Marte’s, McCutchen’s, and Polanco’s DRS totals out as if they had all played full, healthy seasons, you’d end up with a net of 6 DRS.

Meanwhile, if you project the same positional opportunities in 2017 but with the Pirates new alignment and with their expected changes in DRS per 100 opportunities due to the position switches, their net total of 15 Runs Saved is 9 runs better.

In practice, the specifics of the position changes will not play out exactly this way, but it’s clear that the Pirates are making a good decision in principle. And given Marte’s exceptional left field defensive totals, it may be the case that the Pirates have secretly had one of the best defensive center fielders all along.