Legend · Designed 2001
The gyroball
The pitch designed on a computer, mythologized into a monster, and quietly debunked by physics.
Signature pitchBullet spin, zero Magnus
The gyroball is real but heavily mythologized. It was not discovered on a mound but designed on a computer by a Japanese pitching coach and a computer scientist, who modeled its properties and published them in a 2001 book. The legend that grew around it, a "double-spin" pitch that breaks twice and that Daisuke Matsuzaka threw as a secret weapon, is the part that does not survive contact with the data.
The signature pitch
A ball thrown with "bullet" spin, the spin axis aligned with the direction of flight, so the spin never passes over the face of the ball. With the angle between spin axis and trajectory at zero, the net Magnus force is essentially zero: the pitch falls on gravity and drag alone, with no lateral break. Its only honest real-world cousin is the accidental "back-up slider," which shares the same spin signature.
From Nathan and Baldwin’s analysis: "the net Magnus force on the ball is zero. The only forces acting on the gyroball are gravity and drag."
In their words
“I have done it in a game, but not too much. Sometimes accidentally.”
Daisuke Matsuzaka, asked whether he throws the gyroball; relayed from a 2006 Yahoo! Sports piece and cited in the SABR analysis.
The myth, and the physics
The dramatic-break legend is false: with zero Magnus force there is no break to exaggerate. Independent PITCHf/x studies of Matsuzaka’s 2007 pitches reached the same conclusion: the secret monster pitch was not really there. What the gyro idea does, against a hitter expecting a fastball, is fall well short of where the fastball would finish, a heavy, late tumble.
Two independent tracking-era studies reached the same conclusion from different samples. Both are kept here rather than merged.