Spin Direction shows which way the ball is spinning as well as the direction of movement due to spin from the pitcher’s view. Spin Direction is shown as the blue arrow on the Clockface. For fastballs, the Spin Direction is generally close to the pitcher’s Arm Slot, but it can still vary from a few degrees below the pitcher’s Arm Slot to 45 degrees above the Arm or more for cutters.

Spin Direction determines the direction of the movement due to the Magnus force and is one of the key drivers of pitch shape. Raising your Spin Direction will tend to emphasize Vertical Movement, while lowering it will tend to emphasize Horizontal Movement.

It’s important to note that Spin Direction is also closely related to Spin Efficiency. Raising your Spin Direction above your Arm Slot most often results in a loss of Spin Efficiency. A loss of Spin Efficiency results in less overall Movement.

Changing Spin Direction can also have a small effect on Spin Rate and Speed.

The pitchLogic STUFFpL system anticipates all these effects before recommending a change to Spin Direction.

It can be a challenge to find your ideal Spin Direction for any type of fastball. This is because any change to Spin Direction can involve a tradeoff between different priorities. pitchLogic’s STUFFpL can help you find your unique sweet spot.

Raising Spin Direction on a four-seam fastball can improve the pitch by making the movement profile more vertical. This may come with a loss in Spin Efficiency but can still produce an overall more effective pitch. Fastballs with more Vertical Movement are often described as having ‘life’, ‘ride’, or ‘carry’.

Alternately, pitchLogic may determine that lowering your Spin Direction helps produce a higher Spin Efficiency and more overall Movement.

For two-seam fastballs/sinkers, pitchLogic may recommend lowering your Spin Direction to create more Horizontal Movement and/or less (upward) Vertical Movement. This may also increase Spin Efficiency. Pitches with this shape may be described as having ‘sink’ or ‘run’.

Alternately a lower Spin Efficiency can be desirable for two-seam fastballs. A lower Spin Efficiency can decrease Vertical Movement for more ‘sink’ and may also improve your ability to create seam shifted wake movement, which helps create the sinking motion on two-seam fastballs.

For cutters, a glove-side Spin Direction with a lower Spin Efficiency is common. In this range, Spin Direction changes can balance Movement and Speed. Lowering your Spin Direction (toward the glove-side) may improve the Movement but will decrease Speed slightly. pitchLogic’s STUFFpL system can identify which adjustment is most likely to complement each pitcher’s unique skills.

You can alter your Spin Direction by making small changes to your throwing motion, grip, or release.

Although you can change Spin Direction by modifying your Arm Slot slightly, we recommend trying to keep your Arm Slot the same unless pitchLogic gives a separate recommendation to change Arm Slot.

You may be able change the position of your wrist at release point. If you want to raise your Spin Direction (moving the blue arrow toward 12:00), think of keeping your fingers on top of the baseball and pulling down as you release the pitch. You can also raise your Spin Direction by moving your grip toward the outside of the ball and ‘cutting’ the release slightly.

You may be able to lower your Spin Direction away from 12:00 by pronating your arm at release. Think of pointing your thumb downward. Alternately you may be able to adjust the angle of your wrist slightly.

https://pitchlogic.com/metrics/spin-direction