My favorite player helps us understand wOBA.

This President's Day B.J. Upton will help me illustrate the joys of wOBA.

via images.athlonsports.com

First off, what is wOBA?

The formula follows, but here is a brief definition: "wOBA" or Weighted Onbase Average is a statistic used to describe a player's offensive contribution. It is based on the idea that every offensive outcome has a set "run value" that describes its worth. Over the course of a season, game, career, etc. everything a player does offensively is thus tallied using the run values and turned into a rate stat based on Plate Appearances.

Here's the rough formula for wOBA:

((0.72xNIBB + 0.75xHBP + 0.90×1B + 0.92xRBOE + 1.24×2B + 1.56×3B + 1.95xHR + .25xSB - .5xCS) / PA

As you can see, one of the best things about wOBA is that it includes everything. Unlike BA it doesn't ignore walks or hit by pitch, unlike OBP it doesn't count a single and a HR the same, and unlike slugging it incorporates RBOE, SBs, and CS. It really is an all-inclusive look at a ball player's offensive contribution. That's why B.J. really likes it. He gets credit for his willingness to walk. His stolen bases aren't just a tagline at the end, but they're included in valuing his offensive contribution. And guess what, his power (when it returns because we all know it will) gets fully accounted for as well. 

Well now some of you at home (or work more likely) are thinking "Great Ryan! This is a very illustrative statistic, but I still can't tell heads from tails looking at it." This is when our pal Mr. Upton comes in handy. Due in large part to his shoulder injury (I hope) B.J. has a wide variety of offensive outputs that we can look at to examine the scale of wOBA.

In order to set a baseline for scale, remember that Tango created wOBA to resemble OBP. In his words*:

When you look at wOBA numbers throughout the book, just think OBP, and you’ll be fine. In other words, an average hitter is around 0.340 or so, a great hitter is 0.400 or higher, and a poor hitter would be under 0.300.

So with this in mind, let's look at B.J. Upton's career as an illustration of wOBA.

 As we all know, B.J. came up for a brief look in 2004 and provided a glimpse of what he could do offensively. He posted around a league average wOBA in 2004 (actual league average was .330) primarily before his 20th birthday, Unfortunately his defense at the time forced him back to the minors in 2005. In 2004, his offensive output was split equally between his ability to get on base and his ability to get extra bases (i.e. stolen bases and power). This is illustrated by his wOBA being in line with his OBP. The next year, mired with defensive instability he did not produce at the level expected of him at the plate. His .275 wOBA was probably below replacement level as league average was .332. This year, though, we see the trend emerge where B.J.'s offensive value lies largely in his onbase skills. When looking at a player's wOBA if it is above their OBP then they derive more value from their ability to get extra bases (Ryan Howard's career wOBA is .396 and his OBP is much lower at .376). When a player's wOBA is lower than their OBP then they get more of their value from their ability to get on base (Wade Boggs career OBP is .415 and his wOBA is .380).

In 2007 B.J. Upton came up for good and got a full-time gig in the field. His offensive output was a big reward to the Rays as he posted his best wOBA to date (.387) and once again showed that he was an incredibley balanced offensive player (.001 difference between wOBA and OBP). That season thanks to a wOBA .056 above league average he contributed 25.8 offensive runs above average. This shows another great thing about wOBA: it can easily be converted to a measure of offensive runs. To figure a player's offensive runs above average you merely subtract league average wOBA (or .330 as a ballpark figure... pun intended), divide by 1.15 to get rid of the scaling, and multiply by the plate appearances. Voila! Now you see how many offensive runs they provided over (or below hopefully in the case of Sox and Yanks players) the average ballplayer.

Following his breakout in 2007, B.J. had a somewhat dissipointing 2008 at the plate. I believe due to his shoulder injury his power was sapped as evidenced by a similar OBP to 2007 with a significant drop off in wOBA. He was still an above average hitter in 2008 because he did a great job of getting on base, stealing bags, and hitting doubles. 2009 was a different story though. Perhaps it was the lingering shoulder injury or perhaps it was just a tough year, but in 2009 B.J. Upton was below average at the plate for the first time since his brief stint i n the bigs in 2006. He once again got the majority of his value (what little there was) in onbase skills, but it was a relatively poor .313.

Hopefully this year, B.J. will return to .380+ wOBA form, and we can talk about how he put his shoulder injury behind him for good and be the star we all know he is.

Linkies:

*Tango introduces wOBA

Tango expounds on wOBA

Fangraphs is a great source for wOBA and many other statistics. It's also where I got the statistics for this post.

I hope this helps some of the n00bsters around here get a grasp on wOBA and feel free to ask questions in the comments. I'll be around, and I'm sure R.J., Tommy, and maybe even Erik will stop by to answer questions or discuss additional benefits of wOBA.