Why Are Intentional Walks Excluded from wOBA?

Photo Credit: Adam Hunger/Getty Images

wOBA both ignores intentional walks (IBBs) and values hit-by-pitches (HBPs) higher than unintentional walks (uBBs). I’ve frequently had this discussion with my friend and former colleague Rob DeLuca: Can one of our most advanced and run-correlated offensive metrics be improved?

In this analysis, I’ll take a look at all the uBBs, IBBs, and HBPs in 2015-2016, a time when Statcast was separately marking IBBs on a pitch-by-pitch basis, and compare the change in run value for each stat category. My sample contains 27,000 uBBs, 2000 IBBs, and 3000 HBPs.

The change in run expectancy - i.e, the “delta_run_exp” field - is annotated for the uBBs and HBPs, but not for the IBBs. Hence, I used the Run Expectancy matrix illustrated in Table 1 to find the change in run expectancy for each IBB.

Table 1: Run Expectancy of the 24 game states (RE24) in 2022

My results are as follows: HBPs are worth 0.356 runs each, uBBs are worth 0.209 runs each, and IBBs are worth 0.175 runs each. The 2024 wOBA weights for HBPs and uBBs are 0.724 and 0.692, respectively.

In essence, wOBA is undervaluing both HBPs and IBBs relative to uBBs. Batters atop the IBB leaderboard, including Barry Bonds and Ted Williams, were worth even more to their teams than wOBA gives them credit. In addition, HBP leaders such as Craig Biggio, Anthony Rizzo, and Chase Utley have also been worth more to their teams than their wOBAs suggest.