Doc has said many times in the past that he doesn't give players court time, they have to earn it. Even in the earlier blowouts, Doc didn't just toss JaJuan into the game...he didn't *give* him minutes, he made him *earn* them.
How do you earn minutes from Doc? You do it by convincing him that if you are playing that he will know what he's going to get from you. For example, Scal wasn't a great player, but Doc knew what he would get when he put him into the game. That was something he could plan for and count on. Rookies, even second year players, don't have a track record. Doc hasn't seen with his own eyes what they can and can not do on a consistent basis...veterans (even mediocre vets) have. For better or worse, Doc *is* going to favor what he knows over what he thinks might be.
For young players to get minutes they need to show Doc, first in practice and then in games, that they are going to perform (at least) one skill at a consistently high level. Powe, rebounded consistently, he played early. Delonte and Tony defended consistently, they played early. Bradley, eventually, defended consistently at a high level, so he gets to play. We also hear that Bradley keeps hitting "that shot" in practice, but not in the game...but consistent effort (and skill) on defense keeps him in the rotation even it the shot isn't falling, yet. Moore's skill is more his shot than his defense and we hear that he is hitting that shot in practice, so he gets a chance and is great but his shot is streaky from game to game...so he doesn't get *consistent* time on the court, yet. We hear that Johnson has consistently been showing energy and a good shot in practice, so when there is an opening he gets floor time, and he produces. He will get more floor time now, and if he consistently produces he will continue to get floor time, but if he doesn't he'll be back on the bench.
I guess other people don't see, but how Doc operates seems pretty clear to me: a) you have to show him that you possess a skill set that will help the team win games, either in practice or from past experience (veterans), b) you have to show him that skill set, on a consistent basis, in practice, c) then you will get a chance to show off that skill set, consistently, during games, and d) do all the above and you are in the rotation. Fail (a) and you're gone. Fail (b) you sit on the bench and don't play until Danny an get rid of you. Fail (c) you go back to the bench and rarely play.
Added...
Oh, and if you can't master the rotations on defense you aren't going to play for Doc either. That's pretty clear.