Pitch Grips: 2-Seam Fastballs
Two-seam fastballs are often classified by their movement to the pitcher’s arm side and some possible downward sink. They can pair with a straight four-seam fastball to either get a hitter to swing overtop of the two-seam or for them to get on top and hit a ground ball.
The grip for a two-seam fastball involve aligning the index and middle fingers of the throwing hand with the closer two-seams of the ball. This grip varies more than a four-seam grip, depending on hand size, comfort of the grip, arm angle, and desired movement.
Two-seam fastballs are generally thrown similarly to a four-seam fastball, but sometimes pitchers throw them with earlier pronation. (Pronation is when the thumb turns down towards the ground.) This wrist movement can result in more armside run, depending on the pitcher.
Here is some spin-rate information on some of the more popular two-seam fastballs: