I don't doubt that DM is frustrated with missing All NBA and that this is part of this....but holding him out of this playoff game doesn't effect All NBA. He was already a full participant in practice and as I understand practices are just as physically demanding as games. You almost never see a full participant in practice not play the next game.
But like I was saying earlier, it doesn't really matter whose right. If there is no trust between training staff and player, that relationship cannot exist. If Mitchell truly was not ready to play, they needed to do a better job of communicating that to him. That is part of the job.
The fact that everybody was blindsided by this including the other players makes me think that the training staff was trying to show authority. At minimum, it is a total failure of management to have nobody on the team know what the situation is. The training staff could be 100% correct in their call, but if the players didn't know this was the case than it is still a major failure. Somebody is going to lose their job over this, and it's not Don.