Friday, January 21, 2011

The Luck Dragon Revealed: BABIP, LOB%, and HR/FB Explained

In my post discussing the Carl Pavano signing I made reference to a lot of concepts that fans of the game might not understand if they haven't kept up with some of the new-wave statistics that have come into fashion over the past decade.

While I've already written a primer explaining the concept of fielding independent pitching, in the Pavano post I used a number of other metrics - BABIP, LOB%, HR/FB rate - as well. While I did try to explain some of those things within that post, as long as I'm creating a series explaining different sabermetric concepts, it strikes me that this is logical next piece to go with.

We'll start with a quick bit of reflection from the FIP article;

"FIP (or xFIP) is a statistic that attempts to marginalize to the greatest degree possible, the effect of a teams fielders, home ballpark, and the effect of luck from a pitchers performance."

The statistics that were going to discuss today, would be the "luck" component of that sentence. And because I like goofy videos like this, we're going to call it, "The Luck Dragon."

What are BABIP, LOB%, and HR/FB Rate?

• BABIP (Batting Average On Balls In Play) is a statistical measue of how frequently a ball in play (not a foul or homerun) falls in for a hit. Since we in the baseball community have a massive number of nerds who are obsessive about the game we know through their hard work that over the course of history, batted balls become hits about 30% of the time. Therefor we can surmise that when a hitter or pitcher has a BABIP over or under that mark, they have been either lucky or unlucky.

• LOB% (Left On Base Percentage) is a statistic that measures how frequently a pitcher was able to strand runners. As is the case with BABIP, LOB% is a static measure where the average is 72%. And just like BABIP, when pitcher over or underperforms that amount, they can be said to have been either lucky or unlucky. Here's another fun video explaining LOB%.
• HR/FB (Home Run to Fly Ball Ratio) shows us how often a ball batted in the air becomes a homerun. This is getting a bit repetitive at this point, but just like the two measures listed above, we know that this metric has a pretty static rate of about 11%. The difference between HR/FB and BABIP/LOB% is that HR/FB is not always a component of luck. In this case, it can be a combination of both luck and a pitchers home ballpark.

I'm skeptical, shouldn't good pitchers be better at these things?

That would seem to make sense, but the answer is actually no. Take any two pitchers you'd like with at least 1000 innings (five 200 inning seasons) pitched and check'em out. Let's take Livan Hernandez and Randy Johnson. Those two couldn't be much different. Johnson was a multiple Cy Young winner with amazing strikeout stuff and at times spotty control. Hernandez was an inning eating journeyman who struck out very few and gave up hits by the bushel.

Randy Johnson .302 74.7 12.1%
Livan Hernandez .310 72.1 9.5%

As you can see, despite one of these pitchers owning a career ERA of 3.29 and another owning a career ERA of 4.39 their rate statistics are surprisingly similar with the exception of their FB/HR rates. That's likely because no one tracked the rate of fly balls to homeruns until 2002. My guess is that had that metric been tracked for longer, we'd have gotten more similar numbers. Either way, neither are egregiously off the 11% norm.

Still not convinced? Lets take two more, say the human launching pad and running joke that is Oliver Perez (4.63 ERA) and the professor, Greg Maddux (3.16 ERA).

Greg Maddux .289 72.3% 12.0%
Oliver Perez .298 73.4% 11.6%

Ok, maybe you've got something there. I'm listening.

You'll recall that in my Carl Pavano post from yesterday where I discussed the reasons behind his why his ERA fluctuated wildly from one year to the next I cited two of the three metrics listed above.

A pitchers final ERA is actually an amalgamation of his actual performance as measured by his FIP, and our "Luck Dragon" trio of BABIP, LOB%, and HR/FB. A pitcher can perform well with an FIP of 3.75, but see that solid performance ruined by bad luck. Given that I write primarily about the AL Central I have a convenient example in Francisco Liriano.

In 2010, Liriano was the 2nd most "unlucky" pitcher in the game (Jason Hammel was #1) with a 0.96 spread between his ERA (3.62) and his FIP (2.66). On his performance alone, FIP rated Liriano as the 3rd best pitcher in baseball in 2010 behind just Josh Johnson (2.41) and Cliff Lee (2.58). Yet Liriano's ERA didn't support that at all.

That's because his Luck Dragon bit him hard.

In 2010, Liriano was struck down by a BABIP of .340 (4% worse than average) which ranked 2nd worst among all starters (to James Shields .354). He was also adversely effected by his LOB% of 73.1% - though not nearly to the same degree as his BABIP.

These are the exact opposite things that happened to Pavano. The two pitchers ended up with near identical ERAs, but that doesn't necessarily mean the two are equal in talent, and they almost certainly won't be equal in future performance.

And yes, if they ever make the BABIP Luck Dragon video, I'm absolutely going to post it.

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