I honestly dont think Doc Rivers is that good of a coach. He's a good motivator, but not really an X and O guy, or a guy that situationally coaches well.
Look at the Orlando OT loss in the last series where the C's get the ball with around 12 seconds left in the game, tied and they get no look and goto OT. The obvious thing to do is call TO and run a play to get a good shot, but instead they goto OT and lose.
Before Ray Allen, Garnett, Eddie House and James Posey showed up, Doc had those guys playing like the junior varsity. Essentially Ainge brought in vets that could play and Doc managed how they would work together and let them do their thing. Good manager of people that needs a solid X and O guy as his assistant....ie. Coach Tib, who is gone next year.