Variations of the Fastball
The fastball is a pitcher's most important weapon. It provides the foundation for everything else he does on the mound. It doesn't matter if a pitcher's fastball maxes out in the low-80s or hits triple digits - the ability to throw it for strikes is the key to success.
Young hurlers must first master the grips of the four-seam and two-seam fastballs - in that order - before trying more advanced pitches. The four-seam fastball, as the name suggests, is held across the "horseshoe," or the two widest seams of the ball. The grip is the basis for other pitches and teaches young pitchers how spin affects the ball's movement. It also provides maximum velocity on the ball.
On a four-seam grip, your fingertips should contact with the seams, and your thumb should be under the ball. Your fingers should be a comfortable distance apart but not too far - the farther they're spread, the less velocity on the throw. Your thumb should be below, acting as the anchor.
Younger players with small hands might be more comfortable initially gripping the ball with three fingers - index, middle and ring - until their hands are big enough to master the grip with just their index and middle fingers. Either way, your fingers - whether two or three - should go across the seams.
The four-seam fastball consists of a gentle grip and an easy release. Don't choke the ball. The throw will stay straight, which is why infielders use a four-seam grip to throw. As pitchers develop, they may experience some natural movement on their four-seam fastball. In time, this pitch is often used to work the cross-corner of the plate.
Unlike the four-seam, which is held across the seams, the two-seam fastball is held with the seams. For both grips, it's important to have your fingertips rest on the stitches, not on the slick part of the ball. Holding the stitches enables you to pull on the ball, creating friction and backspin.
With a four-seam fastball, more spin means more power in the pitch. With a two-seam grip, spin equals movement. Grip the ball with the seams either on top or with your fingers across the narrowest seams. Pressure on your index and middle finger at the release point will produce added movement. Because of the finger pressure, though, velocity decreases. The key is to maintain consistent arm action and arm speed so as not to tip the pitch.
As a pitcher progresses with this pitch, they may develop sink or arm-side run. Often this pitch will be used to work the arm side of the plate.