"Is he keeping his hands behind him on the bat, even while he strides forward with his front foot? This is usually the sign of a great hitter, who can commit part of his body to a pitch while maintaining sufficient control and arm strength to do you damage at the last split-second. Willie Mays and Roberto Clemente had this superior ability to wait on a pitch with their arms back, even as they stepped forward. There was no set way to pitch them except to vary your pitch selection while remaining alert to signs of particular strengths, weaknesses, or preferences that they exhibited in any given at-bat."