What it is

When we talk about spin, we describe it from the pitcher’s point of view. Sidespin is what you would observe when throwing a frisbee. When the ball is released and the left side of the ball is rotating back towards the pitcher, Sidespin will appear as a positive number. Positive Sidespin is the type of spin commonly associated with a four-seam fastball thrown with a low, left-handed arm slot. When rotating in the opposite direction, Sidespin will be displayed as a negative number.

Why it matters

Sidespin creates a horizontal force on the ball, which creates Movement to the left or right. Positive Sidespin creates movement to the left from the pitcher’s point of view, while negative Sidespin creates Movement to the right. It’s typical for pitchers to have some Sidespin on a fastball; however, pitchers with a lower Arm Slot will tend to have more Sidespin and less Backspin. A fastball with more Sidespin will have more arm-side run. Similarly, a breaking ball with more Sidespin will tend to have more glove-side Movement.

How it is used

There is typically a tradeoff between Backspin and Sidespin, and choosing which to emphasize depends on the type of movement you want to create. If you do want to create more Sidespin on your fastball you can change your Spin Direction toward 3:00 (for RHP) or 9:00 (for LHP), increase your Spin Efficiency, or increase your Total Spin. Pitchers with a lower Arm Slot will often have a Spin Direction closer to 3:00 or 9:00. In general, as a pitcher’s Arm Slot drops on a fastball the Backspin decreases and Sidespin increases.