Last Thursday, Pedro Martinez revealed one of his methods of deception when an opposing runner was on second base – he would change grips mid-delivery.
The rest of the MLB Network Showcase broadcasting team appeared extremely doubtful, so Pedro got out of his chair and showed them exactly how he would switch from a fastball grip (which the runner might have signaled to the batter after seeing the catcher's sign) to a changeup grip in the short time (maybe one second, tops?) between pulling the ball out of his glove and firing it towards the plate.