Sinker

Baseball Pitching Grips - How to throw a sinker: The sinker moves down and to the throwing-arm side. A right-handed pitcher's sinker moves from left to right and has some down movement with approximately 95 percent of the velocity of the fastball. In the sinker grip variation, the thumb slides to the inside of the baseball's center line. Sliding the thumb up the inside of the baseball causes the ball to be held off center, giving it a side-spin that causes sinking movement. The higher the thumb goes up the side of the baseball, the more sinking movement but less velocity it has. Many pitchers slide the thumb up top and use this pitch as a change-up.