Monday, April 19, 2010

I'm In Love with wOBA

wOBA: Weighted on base average.

This is the stat. The stat. If you want to get a hang of a player's overall offensive ability, look no further.

Why I love wOBA, in a nutshell: unlike the OPS stat, which is just on base percentage plus slugging percentage, wOBA takes run values into effect. In slugging %, which just measures how many bases a batter earns per at-bat, a home run is worth four times as much as a single. In On-base percentage, they're worth exactly the same. OPS, which combines the two, does not effectively erase the shortcomings in either stat.

It just doesn't work. The truth is, a home run is worth 1.7 runs more than an out. What that means is that the average of all home runs (tracked over a period of time) produces about 1.7 runs (the majority of home runs are solo shots, worth 1, while some are worth 2, 3, or 4). Just combining on-base and slugging comes nowhere near to reproducing this number, and actually skews largely toward slugging, and hence toward a power hitter.

So you know how sabermetrics people always kinda scoff at speed and stolen bases, and skew toward sheer power? It's because of OPS. Now, there's finally a way to account for valuable assets like these. (In case you're curious, a steal is worth roughly .19 runs.) Not to mention the fact that OBP is a better predictor of run scoring than slugging %.

If you're interested in reading detailed accounts of its development, check here and here and here.

The other great part of wOBA is that they scale it to the on-base percentage scale. So the casual fan can easily read this stat and know whether a player is bad, average, or great based on the fan's knowledge of OBP. There's an easy adjusted stat, too, called wRAA, which stands for runs above average based on wOBA. In other words, how many runs better were all these guys than the league average? Here were the 2009 leaders in wRAA:

Albert Pujols 69.7
Joe Mauer 54.9
Prince Fielder 54.2
Ryan Braun 44.8
Hanley Ramirez 43.9
Mark Teixeira 42.9

But the best part of this stat? It finally gives me an accurate sense of how good Brett Gardner is offensively. Last year, with only 284 plate appearances, his wRAA was 2.0. This year, he's 2.2, with a wOBA of .402.

What this means: Brett Gardner is above average offensively. And he does it with speed. A sabermetric stat has basically just vindicated a speed-first player who wouldn't even be involved in an OPS discussion (in fact, his adjusted OPS last year was 93, which is 7 below the league average). But if you've seen games like last Saturday, when Brett reached base four times without hitting it out of the infield, and followed up with stolen bases and runs scored, you knew he was a worthwhile player. This is sophisticated and awesome.

If you didn't understand any of this post, I apologize. I'm not sure I do, either, but I'm happy. Here's a picture of Brett doing what he does best:

1 comment:

  1. There is a lot of math involved in today's posts. Tomorrow, how 'bout we keep it a little simpler?