our practice looks good. But what is it actually improving?

For years, I judged the quality of a practice by what I could see. Were players making cleaner contact? Were the rallies lasting longer? Were they making fewer mistakes? If the answer was yes, I usually left the court believing the practice had worked. Then the player competed. The timing changed. The ball was less predictable. An opponent occupied space, disguised intentions and created pressure. The player who had looked technically strong in practice suddenly appeared unable to use the...