An Early Look at wOBA Differential

The season is still only three weeks old, and basically anything can happen over the course of 20 baseball games. The Brewers aren’t the best team in baseball, the D’Backs aren’t the worst, and Jesse Chavez isn’t going to win the Cy Young Award. But, at the same time, the most recent data is also the most informative data, and there are some numbers that can have meaning quicker than others. While you shouldn’t care too much about a team’s Win-Loss record on April 21st, we can boil down early season team performance into numbers that a bit more heavily represented by skill rather than randomness.

One of my favorite ways to look at team performance is wOBA differential. It’s basically the same concept as run differential, but strips away the heavy factor that sequencing can have on runs scored and runs allowed. The order of events matters in the outcome of past results, but holds little predictive value, and by looking at non-sequenced results, we can get a better idea of how a team has performed than if we also introduce the timing of those events into the mix.

wOBA differential isn’t perfect, of course; it doesn’t include baserunning, for one, and teams can move the needle a little bit by how often their baserunners advance, but that portion of the game is fairly small relative to everything else. By and large, wOBA differential gives you a pretty good idea of how teams have played thus far. So, let’s get to the numbers.

The A’s might be a half game behind the Brewers for best record in baseball, but no other team in baseball is dominating quite like Oakland. Now, quality of competition has to be considered, as the A’s have already finished sweeps of both the Astros and Twins, and have played another six against a mediocre Mariners team. But, this is what you’re supposed to do to weak opponents; bludgeon them. The A’s are tied with the Braves for the lowest wOBA allowed in baseball and are second in MLB in offensive wOBA, behind only the team that plays at altitude in Colorado. The A’s no-stars-no-scrubs approach to roster construction has left them with a very balanced, deep roster that continues to be remarkably underrated, even as they win year in and year out. If they keep playing like they have, we’ll eventually have to admit that the A’s are really, really good.

Also on the encouraging side of the ledger, Tampa Bay should find some solace here; they might be off to a slow start from a run differential or winning percentage perspective, but their 25 point wOBA advantage is fifth best in baseball. Taking sequencing out of the picture, the Rays have been essentially as good as the Dodgers, and no one sees them as an early disappointment. Even without Matt Moore and Jeremy Hellickson, the Rays run prevention has still been elite, and their overall performance should have produced a winning percentage closer to .575 than .475.

On the other end of the spectrum, this methodology offers little hope for the D’Backs; they really have been atrocious, though wOBA differential puts them ahead of Houston, at least. But the relative placement of the D’Backs and Mets is a nice reminder of how much of a role sequencing can play, especially over small samples. The omission of baserunning is a bit of a factor here, as the Mets have been three runs better on the bases than the D’Backs, but a 50 point negative wOBA differential shouldn’t result in a .500 record. The D’Backs look like a dumpster fire because they’ve been both lousy and a little unlucky; the Mets have been maybe more of a contained garbage fire, but there’s still plenty of potential for disaster laying ahead.

But no team in baseball has won more by doing less so far than the San Francisco Giants. By results, they are 11-8 and have outscored their opponents by half a run per game, but they are 21st in wOBA and and only 12th in wOBA allowed, and it’s not because wOBA is underrating their baserunning, as they’ve been below average at that too. Their success has essentially come due to timely pitching; they’ve allowed a .334 wOBA with the bases empty but only a .283 wOBA with men on base; put runners in scoring position, and it goes down to a ridiculous .250. Basically, the Giants have spent the last three weeks pitching themselves into and then out of trouble. If they want to keep wining, they’ll have to stop allowing so many scoring opportunities, because you can’t go an entire season stranding as many runners as they have so far.

These numbers are still just three week samples, of course, and small samples of wOBA have to be regressed too; these numbers are still measuring what has happened over 20 games, not predicting what will happen over the next 140. But, by taking the sequencing aspects out of run and win differential, this does give us a better look at which teams have actually outplayed their opponents over the first few weeks of the season.

And while we have to adjust downwards for an easy opening schedule, the early results suggest that the A’s are a force to be reckoned with.