Four reasons, two of them obvious, one less and one of them ugly.
#1)Last season Bradley took the starting role from Ray Allen. The decision was first about injury and then, Doc Rivers deciding they had a better chance to win with Bradley on the floor. What grounds did Rivers have for this decision?
The Celtics were 26-11 with Bradley getting the minutes.
Opposing coaches were game planning for his defensive ability and he was still one of the top in the league.
#2)Rondo likes Bradley and they play well together. Bradley is a very aggressive defender helping Rondo's game immeasurably.
#3)The next reason is ugly. The more Bradley shines the higher his trade value. He is the starting 2 because he could be a chip in a super star deal in the future.
#4)Bradley, if he remains, is the future of the Celtics. He is a 21 year old potential star who has made his bones on the one thing the Boston Celtics stand for.....defense.
If he is too hurt to play well, he won't start, once he is ready, Jet and Lee will be part of the one of the better 2nd units in the league.