I get asked about this a lot, and I finally have an answer based on the data reported in our recent Baseball Prospectus article. Here’s my take:
1. Know Your Efficiency
It is hard to generate Seam Shifted Wake effects without some gyro. I recently posted a video that explains why this is.
If your fastball has 100% efficiency, you have a gift. One downside of that gift is that SSW may not be for you. If your fastball or sinker is 90-95% efficient, you are in business. If it is less, you might want to work on that.
In this range, both a 2-seamer and a 4-seamer will gain movement in a different direction from Magnus as shown below. The direction of the SSW force is opposite for the two ball orientations. For a side-arm pitcher, the 2S moves down and the 4S moves up. Another way of looking at this is a 2-seam adds to the inferred axis (an axis based on movement, as was reported everywhere until 2020) while a 4-seam makes it smaller. (Recall 180 is straight up, 0 is straight down).
For pitchers with a high arm slot (as pictured), the SSW movement on a 4-Seam is often described as “cut.” I would note, however, that the same effect gives a lower-arm-slot 4S positive vertical break, and no one would call that a cutter.
2. Learn to Manipulate and Control Your Efficiency
The ability to add and subtract gyro will open up lots of SSW avenues. Until now, there has been a singular drive to higher efficiency, but learn how to dial in how much you want.
When examining hundreds of MLB pitchers in 2020, it is 1) clear that SSW is common and 2) that some pitchers repeat it much more. Repeating a SSW requires a repeatable gyro degree and a repeatable orientation of the ball.
Now, let’s discuss. While there is data to back up much of what I have said here, there is also some conjecture. I’d love to hear what pitchers and coaches think based on their experience.