Calculating xwOBA for 2014 Starters and Relievers Using PA Outcomes

Earlier today I unveiled something that I’ve been working on. The basic premise is that we can look at the ratios for how pitchers ended plate appearances and then use league wOBA rates to come up with an estimated wOBA for each team’s pitching. Basically we’re regressing actual production rates to league averages and just focusing on how often pitchers fall into each outcome bucket, relative to their peers.

Of course if we’re going to do this for teams the next logical step is to look at players where variance and small sample size could really use a good kick in the ass from regression. The population for this will be all pitchers with at least 10 IP last year. Let’s take a look at that:

You can check out the starters and relievers there and you can download the workbook from Googs if you so desire. I’d recommend it because you might be surprised by some of the things you’ll find when sorting each of the various columns. Know that I start with the raw data and then moving left to right convert that to z-scores, ranks, and then ultimately, turn those ranks into a percentiles.

Looking at this by lowest wOBA for starters you shouldn’t be shocked to see the names at the top. JoFer, Kersh, Sale, King, and Karns. Wait, wut? Nate Karns only faced 49 batters last year so this isn’t something you can take to the bank, but he profiled very nicely as a guy that got strikeouts and pop ups without allowing many line drives. We continue down the list and find Alex Cobb at 20th overall with an xwOBA of .277 sandwiching him between Greinke and Tanaka. Dude just continues to fly under the radar, but I’ll bet that this is the year people fall in love with the Cobbler.

Continuing down the list the next Rays starter that we find is Drew Smyly at #60 with a .294 xwOBA based off of his strong pop up, flyball, and strike out rates. Next we come to Jake Odorizzi at #81. He’s another guy that relies on strikeouts, pop ups, and fly balls to get guys out. Sensing a pattern? Next we have Chris Archer at #95. Archie gets more grounders than the last two guys, but he still comes in at exactly average for starters with a .303 xwOBA. Let’s flip over to the relievers.

Two Rays made the top-11, but they’re not in the order I bet you expected. Brad Boxxxxberger came in #4 OVERALL slotting between Sean Doolittle and Andrew Miller on the back of a strikeout rate north of 40%. His xwOBA of .222 trails only the aforementioned Doolittle (.221), Ken Giles (.219) and the Cuban Missile Aroldis Chapman at an unGodly .207. Jake McGee comes in at #11 with an xwOBA of .248 trailing his old buddy Wade Davis (.237) by a decent chunk. Many of the following names shouldn’t be a surprise, but occasionally one will pop out. Maybe that’s a guy that’s a little underrated or had some poor ball in play luck last year. Might be these are some names to stash in the old upstairs filing cabinet.

Keep in mind that league average xwOBA for relievers with at least 10 IP last year was .295. The rest of the pen that pitched last year slots in as follows:

#60 Kevin Jepsen .273 xwOBA

#86 Ernesto Frieri .281 xwOBA

#96 Jeff Beliveau .284 xwOBA

#146 Kirby Yates .295 xwOBA

#267 Grant Balfour .322 xwOBA

Yes Grant Balfour was that terrible last year and it wasn’t just bad luck. He finished just behind Brandon Gomes who threw up (heh) a .321 wOBA. Some other guys from last year’s failpen include #172 Heath Bell at .301. He was in the top-five for groundball rate, but the thing about groundballs is that they go for hits and those things can stack. Flaming pile Josh Lueke came in at #250 with a .318 xwOBA.

It’s pretty late in the season to do a whole lot of dumpster diving, but keep an eye on guys that get cut early from camps. Maybe they’re losing out in a numbers game despite putting up numbers last year that should have looked better than they actually did and this probably acts as a way to get a different perspective of guys than what is being forcefed to you by the fantasy “experts”. Good luck out there and hopefully you find some use for this stuff.

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About Jason Hanselman

Rays fan.
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