http://www.thecompletepitcher.com/baseball_pitching_gri...y_zito_curveball.htm
How Lefty Barry Zito Grips and Throws His Curveball
By STEVEN ELLIS | The Complete Pitcher®
(This article is adapted from a Sports Illustrated article by Ben Reiter, which appeared on CNNSI.com)
NEARLY 150 YEARS AFTER William Arthur (Candy) Cummings invented the curveball, A's lefty Barry Zito (gripping his curveball at right) has come closer than any of his peers to perfecting it. Zito's nose-to-toes breaker is so admired — and so feared — that it's earned him the reputation as having the one of the best curveballs in baseball.
"My dad and I picked it up out of a book when I was 7," he says. "He caught me in the backyard.... Then I threw to a mattress with a painted strike zone on it."
Zito, who was 14-12 in 2005 and won the AL Cy Young Award in 2002, grips the ball with his index and middle fingers straddling the seam. "I want to get on top of the ball," he says. "When I release it, I force those two fingers down hard. That creates the torque on the seams, which causes rotation and spin.
"I also don't want to get my arm angle too high because that will take away the ball's bite — I want to maintain a three-quarter arm slot."
Having relied on the bender as his out pitch since he was 16, Zito has developed a two-out, two-strike routine. When he snaps off a curve that feels just right, he often starts moving toward the dugout after releasing the pitch.
By the time strike three is recorded, Zito is several steps off the mound. That's an unpleasant sight for big league hitters, but even scarier is Zito's own impression of his curve: "I still don't feel like I've mastered it," he says.