With Statcast replacing their radar-based tracking systems with the new Hawkeye (optical-based) system in 2020, what we’re now able to see on the field has taken another giant leap forward. What was once inferred is now being observed and those observations have led to ground-breaking work by Barton Smith, Driveline Baseball, and others in fully parsing the forces in play when it comes to pitch movement.
I highly recommend the above readings (and a host of others) for a more in-depth explanation but here are some cliff notes for those new to the concept of seam-shifted wakes:
Every baseball spins in a certain direction, spinning around a certain axis, resulting in a certain movement. The old method of determining spin direction was to use the movement measured by Pitchf/x and work backward to infer what the spin axis should have been. Or, “the baseball moved this way, it must have spun in this direction”.
Hawkeye’s cameras, however, are able to observe what the spin axis actually is after leaving the pitcher’s hand. When comparing the two measurements (inferred and observed) the deviation between the two can tell whether more forces than the downward one of Magnus are at play.
The work of Smith and at Driveline has centered around how the seam orientation of the pitched baseball in flight is informing those “side forces” and how best pitchers can attempt to keep their seams in the place most conducive for their desired movement. Sounds difficult but it’s certainly possible and pitchers have been doing it unknowingly as long as baseball has been played, playing with and cycling through grips in search of the elusive nirvana that is “I just found one that works”.
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