The Detroit Tigers’ team defense (or lack thereof) has been a relatively hot topic since the team signed Prince Fielder just over a year ago. Most of the discussion focuses on the infield defense where none of Jhonny Peralta, Miguel Cabrera, and Fielder are known for being even reasonable defenders in the field, but the corner outfield was nearly as bad (if not just as bad) as the infield.
It was mentioned when Torii Hunter signed early in the off-season that he’d help shore up that deficiency, but there hasn’t been much at-length discussion about how much impact this one change will make.
The Tigers had nine different players take the field in right last season combining for just about 1430 innings. As a group these nine outfielders combined to be 17 runs below average according to both UZR and DRS (advanced defensive metrics). To contrast that, Hunter played 1112 innings in right and was reported to be 15 runs above average by DRS and 10 runs above average by UZR. Both of those numbers are a little bit above his norms in right field, but if we average out what he’s done the last three years (since he made the switch from center), these two defensive metrics would combine to peg him at about +9 runs per season.
Hunter isn’t going to take over all of the innings in right field — he’s going to see some time off — but if we accounted for something like 1100 innings for him, we could reasonably estimate a 20 run swing in total defensive production at this one outfield position. Of course there’s always a lot of randomness in defensive metrics so we can’t really know if all of these numbers are 100% real, but they do pass the smell test. Brennan Boesch was the primary guy out there last year and he looked really bad and Hunter is universally renowned as a plus outfielder, so the general direction sounds good.
But if the 20 run differential is real, it would have fairly noticeable impact on the pitching staff as well. A 20 run change across a 1430 inning season would equate to a drop in ERA of about 0.13. That’s not going to turn Rick Porcello into a Cy Young Award candidate, but it would be enough to drop his 4.59 season ERA to 4.46 without him having to get any better.
As a team last year the Tigers’ ERA was 0.14 above their FIP. We sometimes say this is because they were “unlucky” but a decent portion of the differential could be explained by poor defense. Simply turning one of nine defensive positions from a big minus to a plus could help bring these two metrics in line.