I don't have discussions with parents about playing time. If I get a call about playing time, I let them know we are doing what is best for the team.
''What is best for the team'' must be defined. I don't know what that means. I agree that if a head coach defines ''what is best for the team'' in preseason (that is, his/her philosophy on how players will be used), and then sticks to that plan, there is no need to have coach-parent discussions about the lineup/batting order. You provided the answer before the season started.
But I do think I as a parent would have the right to question a coach about going back on his word: ''You said before the season that nobody would sit out an entire game. My DD sat out two on Sunday. What's up with that?"