This is from the NYT’s Yankees beat reporter Tyler Kepner
There is a strategic reason, Roger Clemens explained, that he carries a black, hard-shell equipment trunk with him at home and on the road. Clemens insists on putting his gloves in the trunk so they do not get banged up during travel. He wants the leather to be stiff so hitters can not see the movement of his hand as he grips the ball.
Early in his career, Clemens noticed how veteran teammates like Marty Barrett and Dwight Evans could tell what a pitcher was going to throw by reading the subtle movements of his fingers and wrist. Clemens is careful to conceal his intentions, using a glove with no openings that would show any part of his hand or fingers.
Clemens said he tries to never wear long sleeves for the same reason. He might reach deeper into his glove to grip a certain pitch, and he figures that if the hitter sees only skin — not the end of a sleeve — he might be unable to tell when Clemens is changing his grip.
Clemens said he wants the leather in his glove to be soft enough to catch a grounder or a flip from the first baseman, but essentially he wants it firm. If a glove gets even the slightest bit floppy, he said, he will give it to his agent, Randy Hendricks, an accomplished softball player who can use a deep pocket in his glove.