Dissecting Connor Thomas' arsenal from Spin Axis standpoint.

[Terry]

In this article With His Glove-Side Pitches Fine-Tuned, Connor Thomas Makes His Pitch for Brewers' Opening Day Roster written by Jack Stern, Thomas mentioned that

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“Seeing the cutter, seeing their reactions – changing their eyes and kind of a little get-back from the hitter – it gave me so much more confidence just to have the sinker middle away in the zone and be comfortable that I'm going to get the ground ball or get the end-of-the-barrel kind of swing because they have to respect both sides of the plate now. And so that comes from me just having confidence throwing it for a strike, not worrying about nit-picking on the corner and missing away.”

Below is the Spin-Based/Observed Movement plot that I generate mimicking baseball savant's style.

You can think of Spin-Based spin axis as the moment capture by Hawk-eye when releasing the ball. As you can see, all of his pitches come from extremely similar spin axis, based on the spin-mirroring and non-Magnus effect concept, hitters had a hard time differentiating these pitches out of hand. Here's another example that might help you furthur undertand this concept.

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>>1.00<<

One of those players was Spencer Turnbull, who might have the best fastballs to help illustrate the effect seam-shifted wake can have. Turnbull throws a four-seamer and a two-seamer that have the same spin axis on BaseballSavant’s new spin axis illustrator. They don’t move the same, at all, and that provides some deception to the hitter. Here, Turnbull throws the four-seam (red) and the two-seam (orange) to a similar starting location, but where the two pitches end up befuddles Christian Yelich.

Although here's the part I haven't figured out how to explain yet, 

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“From talking to righties that I've been teammates with, they said to me, ‘Just from your arm slot, it looks like it's going 20 inches inside the way you throw it.’ So it may not have a big movement profile, but to the hitter's eyes, it looks like it's bearing in on them, which is exactly what I was trying to do with it, because then that opens up the sinker and the changeup away, and I can truly go expand it to both sides.”

Aside from the similar characteristic like his other arsenal out of hand, Thomas' cutter seemed to have more expected movement than average cutter from his arm slot. Let me know if you have an idea on how to approach this!