It is the direction of the spin axis that determines the break of the ball. A perfectly horizontal axis – corresponding to perfect backspin – would yield a fastball with perfect vertical rise. However, most pitchers tilt the axis slightly. For right-handed pitchers, the fastball breaks upward and toward third base. The opposite is true for left-handed pitchers: Their fastballs move up and toward first base.
For a right-handed pitcher, a curveball spins clockwise as it heads toward home plate, pushing through the air, and slowing by the force of friction caused by the resistance of the air. Because of the ball's spin, air will pass more quickly on one side than the other. In other words, the air will move with the spin of the ball on one side and against the spin of the ball on the other side.

In the final phase of this preventative pitching drill the athletes will both face forward. The athlete performing the shoulder portion of the pitching drill will place the KB Powerbands in their outside hand as they laterally lunge and extend their arm away from their body. During this motion it is important athletes use a controlled motion while keeping the arm extended and moving in a straight line. Athletes need to maintain greater control and a slower pace as they bring the hand back toward the body in a controlled motion.
Launching a great pitch requires good timing, and lots of control during the leg kick. New pitchers tend to fall forward too soon on follow-through, rather than staying on top of the baseball. This balance drill gets pitchers to practice holding their leg kick before full delivery. It keeps the pitcher in a position to maintain control, rather than rushing the follow-through. Slowing down the leg kick will ultimately help a pitcher to deliver straighter, faster balls, with more power and poise.

Releasing the Slider ‘Out in Front maximizes it’s effectiveness.  You are best positioned to finish the pitch and command the Slider to break how you wish. It’s going to break later and be drastically sharper. That what you want in this Dominant Pitch. The more consistently that you do this step, the more consistent your results will be. That’s what coaches and scouts want to see….and I know where you want to be as a pitcher….
House primarily talked about kinematic sequencing, essentially developing good timing in your delivery.  The part that was most interesting to me was when he got into the idea of reprogramming movement patterns, or replacing old movement patterns with better ones His main point was that if you want to make lasting changes, you really need to break it down and go back to the early stages of development.
Place your thumb. Place your thumb under the opposite inside seam of the ball. The further your thumb is from your other 2 fingers, the more the pitch will drop. The closer your thumb is to your other two fingers, the more it will slide. If your index and middle fingers are at a 10 or 11 o'clock position, your thumb should be at a 4 or 5 o'clock position.

Why does a curveball curve? How does a pitcher throw a changeup with the same arm speed as a fastball? Baseball is filled with buzzwords that are often used imprecisely. In this series of articles, Mike Richmond explores the baseball’s motion as it travels through the air: How does it behave, and what can a pitcher do to control it? This article looks at the slider to see what causes its very distinctive break.

Master the "two-seam" fastball. Once you effectively use the two-seam grip and arm motion, creating sinking action on the ball, you will be better prepared to throw sliders. For the two-seam fastball, place your index finger and your middle finger directly on the narrow seams of the ball -- the top of the "U" in the stitching. Put your thumb on the bottom of the ball, on the smooth surface of the ball directly under the fingers. Grip the ball tightly to create friction and movement. Use the same arm motion as on a regular or "four-seam" fastball.
This is a good partner drill to practice with a friend or teammate, as it will give you both an equal opportunity to practice improving your accuracy. Start by sitting cross-legged on the ground, facing each other, about 20 feet apart (gradually increase the distance to 30 feet as you get better). When you start, toss the ball back and forth, aiming at each other’s centers. The less the receiver has to move his arm to catch the ball, the more accurate the pitch.
Do you know a baseball pitcher or someone who coaches baseball? Given the popularity of baseball, there's probably a good chance you know someone who can help you learn to throw a great curveball. Find a pitcher or a coach and ask them to meet you at a local field to give you a few pointers for throwing a great curveball. Enjoy giving your throwing arm a good workout!
Hold the ball so that the u shape is facing you upside down.  If you are a righty do it like this.  Placed your middle finger of you right hand onto the right seem of the upside down u.  place your pointer finger directly beside it.  Place your thumb on the seem on the other side of the ball on the left seem.  Place your ring finger on the bottom of the ball curled up with the pinkey finger beside it.  The pinkey finger should not touch the ball. Here is a picture of the grip.
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The difference between a slider and curveball is that the curveball delivery includes a downward yank on the ball as it is released in addition to the lateral spin applied by the slider grip. The slider is released off the index finger, while the curveball is released off the middle finger. If the pitcher is snapping his wrist as he throws, and the movement is more downward than sideways, then he is probably throwing a curveball or slurve, and not a true "slider".
In this video I share with you how to make a tool that you can use to work on your curve.  What you do is screw two baseballs together.  For the pitching drill you want to throw the balls in a way that they rotate tightly end over end on the axis in which you are trying to get your break.  This tool and pitching drill can dramatically improve your curveball.