I think the Celtics are being like the Patriots: playing time is not part of strategy or image: playing time is earned in practice. Brad is going to start and play whoever helps the team win. Maybe Jaylen Brown will be like Tom Brady: NE had a quarterback before Brady, named Drew Bledsoe. Drew was a #1 pick, Brady was 6th round. Drew lost the starter job only by injury, and later when Brady was hurt Drew did a good job in a playoff game. But the team rightly started Brady, because he was better.
Arguably, Crowder is the second best player on the Celtics 2015-2016: but if you win more with Brown, you start him. If Brown needs to get better, you start Crowder.