March 5, 2013 posted by Matthew Dewoskin

Stats You Should Know: xBABIP Edition

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Adam Jones, OF, Baltimore Orioles

Imagine that there was a tool that would tell you whether a BABIP was truly fueled by statistical variance and a batter was hitting way above his weight class. How useful would it be to not have to pore over ground ball rates, line drive rates or fly ball rates while evaluating BABIP? Very useful. It’s simply easier to look at one number rather than three.

Imagine no more! We have xBABIP thanks to some very dedicated, independent mathemagicians. It’s essentially a number that can take a lot of the guesswork out of evaluating batting average on balls in play. What xFIP is to ERA, xBABIP is to BABIP.  There are different formulas at different websites. The most widely accepted and used is at Beyond the Boxscore and was pioneered by Robert Boden (aka slash12). There are even massive, sortable spreadsheets up at fangraphs. It’s a stat that’s gained serious traction in the sabrmetric community and one that smart fantasy GMs will take advantage of. The formula is actually fairly complicated, but there are quite a few xBABIP calculators that can be found using this easy to use website.

xBABIP factors in GB%, LD%, FB%, IFFB% (infield fly ball %), IFH % (infield hit %) and HR:FB % to spit out a number that is a hitter’s or pitcher’s expected BABIP based on what happened to the baseball after it left the bat. It’s a faster way to do what a lot of fantasy analysts have been doing for a few years prior to it’s development

It was pretty obvious to most people watching that career journeyman Justin Ruggiano was playing way above his head for most of the 320 plate appearances he wound up getting with the Marlins in 2012. He managed to post a .320 actual batting average with double digit steals and homers in limited action.

He posted a crazy high .401 BABIP with 1.08 GB:FB ratio. His LD % was only 20.6%, so it’s not like his BABIP was driven by a crazy high number of line drives. His 2012 xBABIP was only .320, a difference of 0.80. Ruggiano got by on smoke and mirrors and the underlying metrics (13.5% swinging strike %) indicate that he could be in for a big regression should he manage to get a full-time job in 2013.

At the other end of the spectrum was Russell Martin. Martin posted 21 homers as a catcher, but was a drag on batting average with a .211 mark. His BABIP was an anemic .222. That’s a little surprising from a guy who posted a 1.46 GB:FB ratio with a 19.4% LD %. He did hit over his head in the power department with a 19.8% HR:FB ratio compared to his 11.2% career average, but there was no good reason for his BABIP to be that low. Martin didn’t post very many infield flies (9.4% IFFB %) and posted his highest IFH % (7.1%) since 2008 (9.4%).

Well, according xBABIP claims that he hit more like a guy who should post a .312 BABIP than a .222 BABIP. That’s a 90 point difference. Martin could be in for a boost in batting average in 2013, but his power numbers are likely to regress. Martin’s days of double digit steals and homers are likely over, but he could still be a useful fantasy catcher with a batting average much closer to his career average in 2013.

What’s that? These guys are too boring for you? You ungrateful…Fine. Let’s take a look at someone who fantasy GMs are actually excited about drafting, Adam Jones. Jones went from useful guy to full-fledged breakout in 2012. He posted a .287 batting average which is his career high, but not that far off from his .278 career average. His .287 actual BA came with a .313 BABIP. His actual BABIP wasn’t that far off from his career average of .316. Now, this is where this gets interesting. He posted a career high 21.5% LD% with a 1.41 GB:FB ratio. His xBABIP loves that LD % and claims Jones actually still has some room to grow in the batting average department. He owned a .346 xBABIP last year. It’s entirely possible that Jones could break out even further in the batting average department if he can maintain his batted ball rates.

xBABIP is one of the newer tools that fantasy GMs need in their tool belt. It works in concert with actual batting average and actual BABIP to give a clearer picture of statistical variance in batting average. It’s even possible to take it one step further and use the xBABIP numbers to create an expected batting average. There aren’t any sites that offer xBA yet, but the formula isn’t nearly as complicated as xBABIP and can be found here. 


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