Let’s find the best pitch on the Mariners: Intro

Back in the halcyon days of early December, 2019, Eno Sarris of The Athletic strove to identify the “most dominant pitch” of 2019. In that piece, Sarris outlined numerous ways to classify “dominance”, including one methodology, percentage of whiffs in the zone on that pitch, where Mariners reliever Brandon Brennan sat on top thanks to his exceptional changeup.

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A whiff is generally the best outcome for a pitch, but it’s even more impressive when the pitch would be a called strike regardless, and Brennan got a league leading 38.2% whiff rate on 102 changeups in the zone last year. In addition to Sarris’ inspiration, the excellent research and writing by Jake Mailhot on this very site with his Stuff+ series last spring, and our Joe Doyle’s sleuthing to share Seattle’s internal spin rate, movement, and velocity numbers for Mariners pitchers throughout the mid and upper minors, provide an ample baseline for identifying some standout pitches, for better or worse.

I want to look at a number of factors, and because we’ll be working with sample sizes sometimes as small as ~15 innings in 2019, I will be cautious about pushing for any firm conclusions, excepting pitchers who have larger samples to work with. We’ll look at the metrics listed above, as well as a few others, and of course discuss the ways in which things like their usage, role, command, and quality of a player’s other pitches can impact the numbers, and try to arrive at some satisfactory answers. Though Joe’s article gives us a delightful window into minor league numbers, for this exercise I’ll be focusing only on players with MLB data to work off of, to get a more detailed breakdown on pitch-specific numbers.

The first article in this series will look at fastballs, which still made up a plurality of pitches thrown in 2019, even as their majority slips year-by-year. In some circumstances, fastballs make sense to be lumped together, but at times we’ll also break up heaters between four-seamers and two-seamers/sinkers, as well as cut-fastballs, which all have distinct purposes and profiles.

In the interim, I would love to hear from you, both in a simple answer and with your reasoning in the comments, what you think is the best fastball on the Mariners roster?

Quick spoiler: it ain’t this one:

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