If you are new to the idea of Seam Shifted Wake pitches, I recommend downloading and viewing this presentation which is about 45 minutes long. I realize that is a lot of time, but this is a complex topic. That said, I think the presentation is easy to understand.
As some of you know, the Seam Shifted Wake (SSW) effect has made me a fan of gyro. Pure gyro refers to a ball spinning like a bullet or a football (thanks, Tom Tango). Most pitches have some amount of gyro and this is quantified by either gyro angle (0 degrees means no gyro, 90 degrees means pure bullet spin) or by the equivalent terms of “active spin” (favored by MLB and seen on baseballsavant.com) or “efficiency” (seen many other places, including Rapsodo outputs). Since gyro spin does not contribute to the Magnus effect (which makes a spinning baseball break), it is commonly thought to be undesirable and of little use. Some have noted that a pure gyro pitch will gain some non-gyro spin as it falls potentially leading to a very small (but perhaps important) amount of “late break.” You can read more about all of that here.
The thing about gyro that I appreciate it that it presents much more opportunity to have a Seam Shifted Wake. With no gyro, you can do a Looper, and probably not much else. Loopers have less SSW effect than other pitches such as the Discoball changeup or Laminar Express. The separation happens over less of the ball.
With gyro, lots of other SSW are possible, and these often have a separation happening over much of the ball and over 3/4 of the rotation. An example is Jared Hughes’s sinker. Here’s one from his backyard in June, 2020.
Using Trip Sommer’s pitch spin simulator, I estimate these top (y) and front (z) orientations.
Here’s that same pitch in a couple of games.
This one is even better.
Hughe’s sinker has a tilt of 2:10 or so (don’t believe what you see on Savant or Brooks on this number–they still use movement and a Magnus model to infer the tilt and efficiency). It should mostly move glove side and have a small amount of ride. But, it actually accelerates downward like a curveball, although not as much. As the season progresses, look him up on Savant and download his sinkers. Check out az, or vertical acceleration. Anything more negative that 32.17 ft/sec^2 is being pushed downward in spite of the spin pushing up. At this writing, that’s 80% of Hughe’s sinkers in 2020, up from 50% last year.
Now, getting to the point. I have commented previously that the orientation of the ball relative to the axis that is required for SSW depends on how much gyro the pitch has. This post will show that the optimum orientation changes with gyro. The change in orientation is not one-to-one with changes in gyro as I previously speculated, however.
I’m going to use the Hughe’s pitch as a guide and UMBA 2.1 to simulate pitches with different orientations and efficiencies to find the optimal downward movement. This version has the option to vary one parameter and in the following results, I will vary either top (y) rotation or front (z) rotation.
First, we need a baseline. For this pitch, with no seam effects, we get this:
The right side is release, the left side is home plate. The pitch arrives 34.5″ off the ground.
Before getting into the results, this animation may help you understand better what 10 degree changes in orientation look like. Note the changing value of top (y) orientation.
I’m going to look at 80%, 75%, and 65% efficiency. Starting with 80%, here is my UMBANQ input:
Recall this is a sinker and we want it to move down. Let me reiterate that these pitches all have the same axis but different orientations. The changes in trajectory are entirely due to seams.
The best case is clearly y = 0 degrees rotation. A similar run shows that z = –15 degrees rotation is optimal. A couple orientations actually seem to move upward slightly. At lower efficiencies, there is even more potential for upward movement.
I’ve repeated this process for the other two orientations. At 65%, if I keep z = –15 and vary y,
the y = 0 case is now the worst result. If you change your efficiency and do not change your orientation, a SSW pitch can become a non SSW pitch. But SSW is possible over a wide range of efficiencies.
Bellow is the optimal y and z rotation for each efficiency.
80%, y = 0, z = –15
75%, y = 0, z = –10
65%, y = 20, z = –10
As efficiency goes down, the required y rotation increases while the z rotation decreases.
Does this look real?
Well, mostly. If you look above, Hughe’s orientation on a 80% pitch was y = –15, z = –15. According to UMBA 2.1, that should not move very much beyond the baseline. But we know it moves downward based on Savant data.
I believe UMBA is currently able to show us qualitative information. It says that the optimal orientation depends on efficiency and I believe that. It gives an indication of the correct direction of change in orientation that is required as efficiency changes.
We are currently updating UMBA based on more recent results and on fewer simplifying assumptions. Within a few months, we should have improved the model to the point where it can predict pitches.