Cubs Quick Hits: Arrieta’s Best, Worst Zones by xOBA

You might recall the hype around the widespread launch of Statcast in 2015. And if you’re still a little unsure of what exactly that means, it’s “technology (that) precisely tracks the location and movements of the ball and every player on the field at any given time.”

That leaves a lot of opportunities for various applications, among them how a pitcher performs. Below is an illustration of the zones in which opposing batters hit Jake Arrieta the hardest (catcher’s perspective). The values are an expression of expected weighted on base average (xOBA), calculated by exit velocity, spray angle, and launch angle.

The average weighted on base average varies year-to-year, but let’s just use .320 as a baseline.

We can see right away that hitters mashed Arrieta’s low pitches, even those below the strike zone. But if Arrieta threw a two-seamer in on the hands and up in the zone, the hitter wasn’t going to hit it hard at all (i.e., .000 xOBA in top left of zone). And if he threw a slider down and away, hitters had no chance (i.e., .257 xOBA in bottom right of chart). If, however, that slider stayed inside the zone, the hitters typically got good wood on the pitch (1.014 xOBA).

Go to for more cool information and charts on various expected metrics. Andrew Perpetua’s work is exactly the kind of new-age public data many of us have been craving, and you should take notice.

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