October 21, 2013
Revisiting BABIP for Fantasy
Every offseason, there is a hitter or two who is dubbed as a poor bet for next year because of an extremely high BABIP. While the warnings are usually valid, they are often vague and don’t give us enough information. Should we avoid a hitter entirely because of a high BABIP? Or are there circumstances where a strong BABIP hitter might be a decent investment the following season?
Table 1: Top 50 BABIPs 2008-2012
These are the top 50 hitters (qualifiers for the batting title) by BABIP between 2008-2012, sorted by the biggest improvement in BABIP to the largest decrease. Only three hitters improved in BABIP from one year to the next so as you might suspect, there is a good reason that fantasy analysts point to high BABIP as a harbinger of bad things to come the following season.
However, the earnings columns indicate that while there is a typically a drop off, it isn’t extreme. The market already adjusts for the possibility that high BABIP outliers are going to slip, giving these hitters a $3 pay cut (on average). It isn’t quite enough of a pay cut, as these hitters earn $22 on average, but while these hitters do take a loss it isn’t a significant one. Thirteen of these 50 hitters turn a profit for their fantasy owners while another four break even. A 34 percent chance of buying a break-even hitter isn’t great, but it’s not the shellacking you might expect given the prior year’s BABIP.
Rather than simply look at a strong BABIP and write it off as an outlier, I always look at the following factors:
1. What is the player’s track record?
2. What is the player’s expected BABIP (xBABIP)?
(GB X .237) + (FB X .138) + (LD X .724)
Using Johnson again as an example, 25.5 percent of his batted balls in 2013 were fly balls or pop ups, 28.3 percent were line drives, and 46.3 percent were ground balls. Johnson’s expected BABIP (xBABIP) was .349. Yes, Johnson should have fared more poorly in 2013, but a .349 BABIP on balls in play in 2014 would still be very good…and well in line with his career norms.
3. Don’t forget to take speed into account
Bringing it back to fantasy
Table 2: Chris Johnson’s 2013: xBABIP versus BABIP
Johnson had 514 at-bats in 2013, only 400 of those at bats resulted in an outcome that put the ball in play (home runs and sacrifice flies do not count against BABIP). Even with a sharp drop for Johnson in BABIP, he only would have lost 18 base hits. There is no way to know how many runs or RBI Johnson truly would have lost, but since Johnson had 11 percent fewer hits on the xBABIP model, I took this percentage of RBI and runs away from Johnson on plays that did not result in a home run.
This rough model tells me that Johnson is extremely unlikely to earn $21 again in 2014. However, it also tells me that Johnson is unlikely to simply disappear fall off of the map entirely. His line drive rates support a strong BABIP and there’s a good chance that he could still put up a decent batting average in 2014, even if it isn’t a great batting average. Most of Johnson’s lost value will come at the expense of his batting average; three of the five dollars he would lose in this scenario would come due to the batting average drop off. On the other hand, there is a good chance that Johnson could still be a positive batting average earner.
There is no doubting that BABIP is an important component of future player forecasting. However, BABIP often gets overstated in terms of how overvalued or undervalued a player is. Typically, a BABIP drop leads to a moderate drop in a player’s production, not a significant one. In cases of significant performance drops, a BABIP decline is merely one contributing factor, not the sole determinant of future value.