Early on my son rarely showed emotion outwardly. As his parent I knew when he was stewing, but few else did. When he made a mistake his face did not change. Some may have perceived that as not caring. Nothing could be more far from the truth. If a teammate or parent watching would have made comments or critiqued him for lack of caring, it would have thrown him off and been innacurate.
Fast forward to first year in college. In the middle of a rough inning the coach yanks him and comments that by wearing his emotions on his face, he was giving the other team an advantage. I,of course, agree with coach.
HOw much a player cares about his own performance and the performance of the team is not necessarily measured accurately by others. Showing your emotions does not necessarily give you an advantage.