A very common mistake with the slider is trying to guide it instead of throwing it. When you do that, your body language changes, your tempo changes, and hitters can read it before the ball even leaves your hand. Hitters read rhythm, effort, and posture. If your fastball looks aggressive but your slider looks careful, you’re tipping the pitch. That’s why many sliders get hit, not because they’re bad, but because they’re obvious. Every pitch must look the same. Same rhythm, same energy, same deli

How to Throw a Slider - The Definitive Guide for Pitchers

Sliders and Movable Points