Getting Dirty With Stats – Evaluating Batters With wOBA and wRC+

Getting Dirty with Stats

Intro | Batting 1 – Linear Weights

Who’s ready to get dirty with some more stats?! Whooo! Today we’ll be putting on our Ice Cream Gloves and finish our discussion on evaluating hitters.

When we last spoke, we settled arguments on message boards across the Internet using linear weights to figure out the run value of all the things batters can do. Remember that? Those were good times.

For the next 20,000 words, I’ll be painstakingly calculating the run value of every unintentional walk, hit-by-pitch, single, double, triple, and home run, for every player in Padres history LOL JK. That’s been done for us already by Tom Tango, a guy whose name you’ll hear a lot the more you read into baseball analytics.

Tango published The Book in 2006, which provides answers to a lot of common discussions about optimal baseball strategy. He also introduced wOBA, a rate stat sort of like batting average, on-base percentage, slugging percentage, or on-base plus slugging percentage (OPS). But those four stats only guess at the relative importance of different things hitters do. wOBA uses linear weights do determine the exact value.

wOBA is set to the same scale as on-base percentage and stands for “weighted On-Base Average” which I find unnecessarily confusing. Chase Headley’s wOBA this year was .330.

It’s important to know what wOBA is and where it came from, but it still isn’t everything we need it to be. One of the goals of this series is to separate things batters are and aren’t responsible for, and you may recall from last time that two big things they’re not responsible for are the ballpark environment they play in and the pitchers, defenders, and peers they play against.

Enter wRC+, anotherĀ portmanteau of sorts that stands for “weighted Runs Created+.” Originally based on Bill James’ Runs Created, the newest version of the stat is based on wOBA, but we’re getting esoteric so it’s best not to worry much about this paragraph.

Ok new paragraph, and here’s the deal: wRC+ is based on wOBA and adjusts for the hitter’s home ballpark and league. Since the game changes across different eras, wRC+ adjusts for year playing as well.

It is scaled so that 100 wRC+ is average, a 120 wRC+ is 20% above average, 90 wRC+ is 10% below average, and so on.

wRC+ isn’t perfect. Not all batters in one league play the same teams thanks to the unbalanced schedule, for example. But it accounts for a lot of important factors that are outside of a hitter’s control, which is extra important Ā for us to consider since our Padres play in an extreme ballpark. It’s also important to keep in mind that wRC+ and wOBA are rate stats, so you’ll need to account for playing time and sample size (which I hope to talk about soon).

That’s about it! Now the next time your buddy compares a player’s OBP in Petco Park with a player who plays in Chase Field (which notoriously favors batters), you’ll know how to keep things fair on both sides with wRC+.

Printed below are the top 5 Padres’ wRC+ from the 2013 season, courtesy of Fangraphs. Remember–rate stat!

Padre wRC+
Carlos Quentin 143
Tommy Medica 140
Will Venable 122
Chase Headley 113
Everth Cabrera 113

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