Doc worked with numbers. He worked with his numbers. Numbers that are not kept by statisticians. Balls deflected, penetrations stopped, rotations executed improperly, three pointers closed out on that were missed, average time the ball crosses half court, average time defense held team to last minute desperation shot, number of times shot clock ran out, average time for the offense to start their set, number of shots taken out of the flow of the offense, etc, etc.
My guess is Stevens has similar and sometimes different numbers he will concentrate on.
Also, as I have been saying for years, coaches develop young players in practice and they reward the player with earned playing time. That's how coaches coach.