THE MYSTERIES OF THE GYROBALL are illuminated by the Slate's Explainer, including the pitch's shared traits with the equally enigmatic googly:

Whether it has a sharp break or a big dip, some major leaguers and pitching coaches have dismissed the gyro as merely a variation on the cut fastball. The gyro has also been compared to a cricket pitch called the googly, which is also thrown with sidespin.

It's unclear whether Matsuzaka actually throws a gyroball. He's been evasive in interviews, saying that he might have thrown the pitch "sometimes accidentally." Carroll believes he saw Matsuzaka throw a few gyroballs during this year's World Baseball Classic. According to Himeno, at least two other Japanese pitchers use the pitch.

Hope the pitcher – and the pitch – are worth it.