Supposedly the Split-finger is suppose to 'tumble' or drop as you can find in most references to the pitch. But it's almost impossible to find the answer to "why?" (perhaps because baseball pitchers aren't physicists?) But I have a theory. It involves knowledge on the way the curveball (12-6 curveball) and the knuckle ball are thrown. So I'll give a brief summary of those two: The 12-6 curveball is suppose to appear to rise to what looks like the 12 o' clock position of a clock (from the pitcher's view) and drop drastically to the 6 o' clock position. The reasoning behind this is pretty solid. Forward spin is imparted on the ball by the pitching delivery, and an area of low pressure is created below the ball, causing it to dive. The knuckle ball is thrown with the least amount of spin as possible. Some pitchers have been known to throw a pitch 60'6" with only one half of a spin. The point is of course for an unpredictable, sometimes 'wiggling,' motion on the pitch. But to relate this to the Split-finger, the delivery is unique. The desired technique for the knuckleball is to create three points on the baseball where your fingers touch the ball, effectively allowing the pitcher to push the ball with as little spin as possible (usually thumb on bottom left of the ball, two knuckles on the top and ring finger on the bottom right creating an equilateral triangle for pressure points) Now the Split-finger: my theory is that the way it is gripped; thumb on the bottom, and index and middle fingers spread on the top right and top left of the ball, allows for an almost knuckle ball like release, only with a little bit of backspin. Once the ball has a slight backspin, the bottom of the ball will have a higher translational velocity through the air, causing a greater air drag force and thus imparting a delayed forward spin on the ball. This causes the ball to wiggle a bit through the air (as seen by batters and pitchers) before the imparted forward spin during the moment of little spin, but tumbling at the last instance due to the magnus force of the curveball like spin. Thoughts? Does anyone find my physics preposterous?