Agree with the Titanic analogy.
The reason that I have heard from talking with some associated with the team is that DO was the one guy in practice who pushed himself and others, meanwhile Diarra practiced hard but missed some time nursing the knees, and the others just haven't learned/understood that practice makes a difference. Also heard that Cobb started the season as a practice beast but slowly started to trend down as his game time dwindled due to fouls/mistakes and bonehead plays
AB was a different case - at 7' he should have cared enough to work on those aspects of the game he needed but the guy, from reports, was not a hard worker during the off season