I was recently sitting next to an NBA scout watching some very talented 18 year old players. One player kept on making great plays and was piling up the points. The scout never said a word about this player until he pouted after not receiving a pass when he was open. His immediate response was "did you see his reaction" - "BAD ATTITUDE".
Your body language says everything when you are on and off the court. If you are not willing to get in a stance on defense, it must be assumed you are not interested in helping your team defend. Coaches can't coach attitude and energy, it's on the player.