The slider is an off-speed pitch that can be valuable to any pitcher's arsenal. It's a pitch that starts out looking like a fastball but moves to the pitcher’s glove side. It can fool hitters and induce weak contact or swings and misses. In this blog post, we'll dive into what a slider is, which pitch metrics are most critical to its success, and how pitchers can improve its movement.

What is a Slider?

A traditional slider is a breaking pitch that is thrown with a grip that is similar to a fastball but at release a pitcher pulls down on the arm side of the ball rather than staying behind the ball. The resulting movement of the pitch is a sharp, late-breaking horizontal movement to the glove side, and depending on the arm slot of the pitcher, hitters may also perceive it as having some sink compared to a fastball since it has less ride. All this movement can be difficult for batters to track and hit.

Some sliders use variations on the grip to create larger, sweeping movement. Others have very little movement at all, but rely on having less ride than the pitcher’s fastball.

Critical Pitch Metrics for a Slider

There are several critical pitch metrics that pitchers must pay attention to when throwing a slider:

1. Spin Direction: Sliders typically have a mostly horizontal spin direction. Think 8:00-10:00 for a right-handed pitcher or 2:00-4:00 for a lefty. Pitchers with very high or very low arm slots are more likely to have sliders with spin directions outside of this range.
2. Spin Efficiency: Sliders typically have the lowest spin efficiency of any pitch type. Most sliders have a spin efficiency lower than 50% and some are close to 0%.
3. Arm Slot: It’s critical for the pitcher’s arm slot to remain similar to their fastball delivery. An effective slider depends on being hard to distinguish from a fastball.
4. Velocity: While a slider is typically slower than a fastball, it's still important to have enough velocity to give the appearance of a fastball and create a late, sharp break.  The ideal velocity for a slider is typically around 5 - 8 mph slower than the pitcher's fastball.
5. Movement: The movement of a slider refers to how much the ball breaks or curves as it approaches the plate. A good slider should have a sharp, late-breaking horizontal movement that fools the hitter into chasing a pitch out of the strike zone. Pitches with a relatively small amount of movement (say 6-12 inches) are often perceived to break late.
6. Location: Finally, the location of a slider is critical for success. An ideal slider should appear headed for the strike zone and then break down and away, which can induce swings and misses. Those thrown in the center of the strike zone are more likely to be hit with high exit velocity.

How to Improve Slider Movement

If you're looking to improve the movement of your slider, there are several techniques you can try:

1. Adjust your grip: Experimenting with different grips can have a significant impact on the movement of your slider. For example, moving your grip more to the outside of the ball may help to create a more horizontal spin direction.
2. Supinate your wrist: Supinating your wrist on release can also increase the spin rate and movement of your slider. This involves twisting your wrist outward as you release the ball, creating more rifle- or gyro spin and causing the ball to break more sharply. Some mental cues for throwing a slider include, ‘throwing it like a football’, ‘pulling down on the side of the ball’, and ‘throwing a sideways curveball’.
3. Alter your arm slot: Changing your arm slot can also affect the movement of your slider. A lower arm slot can produce more horizontal movement, while a higher arm slot can result in more vertical movement. This adjustment should only be used sparingly. A small arm slot deviation from your fastball (maybe 30 minutes on the clock face) may be difficult for a hitter to detect, but a large difference will make it easy for hitters to see your slider coming.
4. Use STUFFpL for personalized recommendations: Each pitcher has different strengths and weaknesses. Your ideal slider depends on a variety of factors, including your arm slot, how it pairs with your fastball, and your ability to create spin. STUFFpL is built into pitchLogic and can help you determine which adjustments are right for you.
5. Practice, practice, practice: Ultimately, the key to improving the movement of your slider is practice. During flat ground and catch play work on adjusting your grip, wrist action, arm slot, and release point to get the movement you want. As you get more comfortable, start using it in bullpen sessions to master the pitch.

The slider can be a great addition to any pitcher’s arsenal. To get the best results, focus on one metric at a time, because they are related. For example, higher velocity will increase the spin rate and a lower arm slot will increase horizontal movement. 

By paying attention to critical pitch metrics such as spin rate, velocity, movement, and location, and the techniques that enhance them, you can improve the movement and effectiveness of your slider. Remember, practice makes perfect, so keep throwing that slider and watch it become a devastating weapon on the mound.