One of the most common fatal flaws for young pitchers is a slow and deliberate leg lift followed by late rapid arm acceleration. The pitcher ends up throwing the ball in the dirt to the extension side on a regular basis or ends up peeling off to get the ball moving in the right direction. Think about a transmission. If you change gears at the right time and maintain a steady rate of acceleration, the car moves smoothly through the gears and you can reach your top end in the most efficient way. If you try to go from 1st gear to 4th gear on one shift, the engine bogs down and you’re wasting a lot of gas. You aren’t helping your transmission and you aren’t getting to the top end in any desirable way.
From the time you take your rocker step, each additional motion in the delivery should be faster and more aggressive. It must still all be smooth and under control and can’t be herky-jerky. People confuse ‘slow’ for ‘in control’ all the time. Fast movements can also be smooth and in control. If your rocker step doesn’t set you up to be aggressive into your lift, then you are not getting anything out of it.
Also, breaking your hands more quickly…but as late as you can, will accelerate your arm from the beginning of its motion instead of accelerating it consciously after coming to the cocked position. At no point does your arm get “up to speed.”