When a pitch is thrown, it typically has four types of spin – Back/Top Spin, Sidespin, and Riflespin (aka Gyrospin). Backspin makes the ball rise or ride up on a hitter, while Top Spin makes the ball sink as it approaches the hitter. Sidespin causes the ball to move left or right depending on the direction of the spin. Finally, Riflespin by itself does not create any movement on a pitch. Think about it this way, when a rifle is shot, the bullet spins so that it flies straight and a football spirals with Riflespin to make a pass travel straight.

Are you wondering how a baseball can spin in three directions at the same time?  In reality it doesn’t.  The ball actually spins on one axis.  So, it’s just a matter of perspective.  Take a look at the following illustration.  With perfect Backspin the ball is spinning around a horizontal or 9:00 – 3:00 axis.  If we rotate the axis so that we can see the side of the ball, we pick up some rifle spin.

Now let’s look at a more practical example.  A pitcher throws a 4-Seam Fastball and keeps his hand perfectly behind the ball at release.  It might spin similar to the illustration below, since no pitcher throws perfectly overhand with a 12:00 – 6:00 spin.

In this example, the pitch has 12:30 – 6:30 spin.  The spin axis is tilted slightly, so that it has mostly Backspin and a small degree of Sidespin.  Since you can’t see the side of the ball from the pitcher’s viewpoint, there is no Riflespin on this pitch.  This means it has 100% Spin Efficiency.

Now imagine the ball being thrown where the fingers come off the side of the ball so that it spins a little like a football.  The more it spins like a football, the more Riflespsin it has and the lower the Spin Efficiency.  (A perfectly thrown spiral with a football has 100% Riflespin and 0% Spin Efficiency.) This does not mean that Riflespin is a bad thing.  Some Riflespin is needed to throw a Cutter as shown below.