Expected Walk Rate Complicates Early Attempt to Explain Jake Arrieta’s Inconsistency

The Jake Arrieta saga never ceases to confuse me. And it’s only getting more confusing.

While we just talked about how Arrieta’s command (as measured by called strikes above average) was ranked in the bottom tier of MLB, Mike Podhorzer’s recently updated xBB% suggests Arrieta’s walk rate actually should have been 1.1% lower in 2016. So how do we reconcile two conflicting truths? I don’t know. This contradictory stuff has me like:

But let’s talk about this more.

I impatiently watched the majority of Arrieta’s starts last year, hoping to see flashes of the 2015 Cy Young winner. And there were times he indeed burned with that familiar intensity, though too often the white-hot glow would flicker and fade immediately thereafter like the dying light bulb in my ceiling.

Looking at it anecdotally, I tend to believe that xBB% simply isn’t accounting for Arrieta’s extreme in-game inconsistency. And that makes sense; even the most robust and reliable stats need a little time to settle and can’t easily or responsibly be applied to individual games.

In the not so distant future, I will dive into a comparison of Arrieta’s in-game release point consistency between 2015 and 2016. For now, though, let’s just dip our toes in the water. Just by glancing quickly at the graph below, we see that Arrieta was far more inconsistent last year than in his Cy Young campaign.

I know this can be intimidating for those who aren’t familiar with deciphering such things, but it’s quite simple if you know what to look for. See those vertical bars extending from each dot? The taller the bar, the more inconsistent Arrieta’s release point. This data is between months, though, and my ultimate goal is to focus on in-game release points. Stay tuned.

Again, this is all being done in the interest of trying to find out why Arrieta’s performance, not to mention the statistical assessments of it, was so inconsistent. If any of you out there have any other ideas, I’d love to hear them.