I’m going to be honest with you: I have my misgivings about advanced defensive metrics—especially those that are publicly available to schmoes like you and me. 1 It’s not that I think the methodology behind these stats is flawed or that the approach itself is a silly one—it’s just that all these metrics seem a bit too reliant on two somewhat flimsy inputs.
First, there is the simple problem of sample size: it is unlikely that a single player will accrue enough defensive opportunities on different sorts of batted balls in a given year to give us a realistic impression of what his actual skills are. It’s been said that you need three years of defensive data—I assume playing almost every day—to make up for this paucity.
The second dubious input problem has to do with the data collection itself: the defensive metrics all rely on “stringers” who are actually at the game and tasked with classifying batted balls into categories. For example, was that ball that Shelley Duncan gracefully tripped for a liner or a hard hit fly ball? Maybe it was a fliner? Who knows? Which sector of left field was it hit to, section 32 or 33? Sometimes these stringers are allowed to record data only at their home ballpark, which can introduce all sorts of biases into their data collection. In short, this is a tricky business and particularly prone to human error.
Really though, it’s all we have. Even though we clearly don’t have the best data out there, we are light years ahead of where we were just ten years ago with respect to measuring individual player defense. The reason, of course, that I lay out such a long-winded introduction to the state of current defensive metrics is that I want to briefly consider some of them, especially in regard to our outfield makeover.
I believe it’s fairly well-accepted that our outfield defense should be improved this season. For one, we’ll have something resembling an everyday left fielder, which is a great start. For two, all three of our outfielders have spent considerable stretches of their careers (in some cases, their entire careers) playing center field, typically a sign of elite defensive talent. For three, there will be none of this, as much as we may well miss it.
All of those are sort of subjective measurements though. It’s great to think we’ll be improved defensively, but really, how many more games might we win because of that improvement? This is where we have to introduce those defensive metrics, warts and all.
So first, I tried to grab both total zone rating and UZR (two different ways to skin the same defensive cat) for the guys who played OF for us last season. I left a few guys out who played very sparingly (Jason Donald, Brent LilliPUTIANbridge), but for the most part, these are the guys who roamed the power alleys for us last year, along with two measurements of how many runs they saved or (more often) allowed compared against the average player.
Some stalwarts may be surprised to see how terribly Choo and Brantley played. I’ve heard pundits occasionally laud both for their defense, but it’s become more and more accepted in recent years that Choo had only one strength (arm) with quite a few weaknesses (range, first step, going back on balls), while Brantley still profiles as a below average center fielder due to his average range and below average arm. It should be noted that he looks just dandy2 in left, as his weaknesses are less pronounced there and the average left fielder is much worse defensively than the average center fielder.
Anyway, these metrics suggest that our outfield allowed 20 to 30 more runs than the average MLB outfield would have over the course of the 2012 season.
Now let’s look at what our new outfield will look like. I had to make a few assumptions here. First, I looked at a player’s entire career and did my best to limit it to the particular position he’ll likely be playing in 2013 for the Indians. So for instance, I looked only at Brantley’s performance in LF over the course of his entire career. In Stubbs’ case, this wasn’t possible, as every inning he’s played defensively has been in center, despite that fact that he’ll be moving to right for the Indians. I’d therefore consider this a somewhat conservative estimate. Balancing that conservatism, we’re assuming that whoever fills in for these guys on their off-days will be average defensively, which is likely a stretch. Hopefully these two assumptions balance each other out. Anyway, here’s the data:
|Drew Stubbs (OF)||3.9||13||8.5|
|Michael Bourn (CF)||10.7||10||10.4|
|Michael Brantley (LF)||3.3||8||5.7|
Granted, this methodology isn’t perfect, but just by taking the average of the two most accepted publicly-available defensive metrics suggests that our new outfield could be a net improvement of around 45 runs, which would result in four to five more wins, strictly from improved defense at three positions.
There are all sorts of caveats here that I’m not going to get into. Michael Bourn could lose a step as he enters his 30s. Drew Stubbs may not adjust well to right field. The defensive metrics may be flat out wrong. Or injuries, MY GOD THE INJURIES!!!
But using the data we have available, it’s possible that without swinging a bat or stealing a base, our new outfield could win five games strictly by turning batted balls into outs at a more efficient clip than their collective predecessors. That’s at least something for our pitching staff to dream on.
AP Photo/David J. Phillip
- Craig just got back from the Sloan Analytics Conference, and I’m dying to talk to him about it. One item I’m hoping to discuss is the movement toward proprietary, team-housed analytics, especially in regard to defensive valuations in baseball. This is where it’s going, methinks. There was a decade or so where the schmoes were outsmarting the teams, but I’m pretty sure that’s over now. They’ve bought out the geniuses and their IP, and moved it behind closed doors. The “Moneyball Era” was exciting. But let’s face it: it’s over. [↩]
- Marte [↩]