From Jonathan Judge at Baseball Prospectus on November 9, 2015:
Recently, we overhauled our approach to how we evaluate passed balls and wild pitches here at Baseball Prospectus. It started innocently enough, as an attempt to make our data better-behaved, but progressed to a gradual recognition that we—and as far as we can tell, plenty of others—have been taking the wrong approach to these events for quite some time. Today, we’ll talk about what we’ve learned, and how our models are much the better for it.
It’s no secret that some catchers are better at blocking pitches than others. Yadier Molina seems to be pretty good at it, and Mike Zunino does not. But raw wild pitch and passed ball numbers can be unfair. The catcher, after all, is not the one throwing the pitch, and some pitching staffs are wilder than others, particularly if those pitchers like to throw certain pitches in certain places. The sabermetric community’s longstanding skepticism of official scoring has also led to the practice of combining passed balls and wild pitches for modeling purposes, even though the former are judged by the scorer to be the catcher’s fault, and the latter to be the fault of the pitcher.
As with all things sabermetric, the means of adjustment for these factors have become more sophisticated over time. At the simplest level, we could simply trust the official scorer, and assume the other factors largely balance out. A more sophisticated approach is the “With or Without You” method, which grades a catcher based on how he does without certain pitchers, or how pitchers do without various catchers. Going one step beyond, researchers have tried to identify relevant factors driving passed balls and wild pitches, incorporated them into models of “likely” passed ball/wild pitches versus “actual” such events, and then grading a catcher on the difference. FanGraphs has adopted a model created by Bojan Koprivica as the basis for its Runs per Passed Pitches (RPP) metric. (The parameters of that model appear to be proprietary, although Bojan does describe the relevant aspects). Finally, we unveiled our own blocking model last year, called “RPM WOWY”: a combination of PBWP likelihood, as determined by PitchInfo, followed by a WOWY assignment of credit among catchers and pitchers.
Read the full article here: http://www.baseballprospectus.com/article.php?articleid=27849
Originally published: November 9, 2015. Last Updated: November 9, 2015.