This article is part of our The Z Files series.
Much like exit velocity needs to be considered in tandem with launch angle for maximum benefit, spin rate and spin axis are necessary to get the whole picture. This discussion will be more of a survey piece, dealing mostly with spin rate. For those interested in the physics behind spin rate, spin axis and pitch movement, please read A DEEPER DIVE INTO FASTBALL SPIN RATE and the associated linked pieces posted on DRIVELINE BASEBALL. The bulk of the information referenced on spin rate and axis in the next few paragraphs is from those postings.
It's generally assumed the higher the spin rate, the better. In many instances this is true, but not all. The effect varies between pitch classifications. The average spin rate for different pitches will be examined later.
Big picture, spin rate and spin axis work in concert with gravity to enact pitch movement, both laterally and vertically. Obviously, gravity always acts to pull the ball downward. Spin rate and spin axis affect air pressure and movement, sometime forming a cushion countering gravity, other times acting as a funnel guiding the ball side to side.
Many equate higher spin with greater movement, but the opposite is true with a fastball. The backspin on a four-seam fastball induces a magnus force counteracting gravity, lessening the