A coach has only a tenuous grasp on the game. He stands on the sidelines, yelling instructions or gesticulating at something and praying his players heed him. Surely, some of the things he says to his team register as the purest white noise—you try modifying the way you do your job on a second-to-second basis according to someone else's frantic direction. But the coach says the things he has to say anyway, because it's all he can do in the moment. This is all he can do, because, from one moment to the next, a coach is more spectator than participant. This is why some coaches flail around like angry, hair-gelled kites in a gale. It kills them that they can't control their players as if they were holding a Playstation paddle.
Rick Carlisle is the calm sort, as people in his profession go, which is to say that he's still pretty loud and animated but generally doesn't appear to be dying of asphyxiation. He's a measured tactician, and a good one. Carlisle understands that the best way for him to exert control over a game is to devise a scheme and drill his team in it ahead of time such that when the game comes, the players may not do everything he screams for them to do from the bench, but will at least play the style he teaches them to play.
And Carlisle's style is one to behold. Under his stewardship, the Mavs have been one of the most aesthetically interesting teams in the NBA. Players are empowered to go off-script as they see fit—Monta Ellis steps into a pull-up three because he's feeling himself slightly more than usual; Dirk Nowitzki kills the ball at the elbow and studies his opponent because Dirk does what he wants—but the offense's default setting is one in which screens and passes abound. More than anything, it moves. If the paradigm for NBA defense is five guys on the string, the Mavs offense is five guys as a wave: they build, crest, crash, and reform as one, sometimes three or four times in the course of a single possession.
Rajon Rondo, on the other hand, has his own ideas. He always does and always has, and this is both the problem with him and what makes him special. On its face, the trade that brought Rondo to Dallas instantly made the Mavericks better, but even at the time there were concerns about how he would fit into the team pass-and-screen-and-move-and-pass offense. As it turns out, those concerns were well-founded. The Rondo-Monta backcourt doesn't work, in large part because Rondo can't shoot, when he's off the ball, his defender is able to help liberally and cheat into the passing lanes.
That's the schematic problem. Rondo's self-belief is the broader issue. Hubristic basketball players tend to think they alone are their team's best chance to do whatever needs doing. They insist upon taking the last shot, on defending the opposing squad's best player. Rondo's hubris manifests itself differently. He sees himself as a literal star, in the least metaphorical and most astronomic sense: his gravity controls everything around him. He is an offense's fulcrum, its director, its engine. He has confidence in other players to make plays, but he needs them to make those plays on his terms, in response to his actions, in the shape of his vision. He is a player who makes assists seem selfish, as if he is saying look how great I am making you as he drops the ball off to a teammate. Rondo gets upset when the people around him can't get on his wavelength, and he's loath to get on theirs. He's great, and as difficult as anyone else aware of that fact.
Unfortunately for Rondo, the Mavs' offense has one author, and it's Rick Carlisle. There's a system in place that allows for players to express themselves, but the system itself is fixed—it can be tweaked, but not fundamentally altered. Rondo is adapting slowly or not at all because he hasn't given himself over to a system in quite some time. Since assuming dominion over the Celtics as Garnett, Pierce, and Allen aged out of the picture, Rondo has only ever operated in a team that operated around him. He had clashes with Doc Rivers, but since he was the Celtics' best player and primary ball-handler, he held a sort of trump card. Rondo's desires were paramount because he was the squad's integral component.
In Dallas, his role is less crucial, and he's dealing with that reality by sulking and sniping. He's arguing with Carlisle on the sidelines, then arguing at length once the two return to the locker room. This is a prosaic case of two strong-willed men locking horns, maybe, but it's also a struggle for what the Mavs are and how they will or won't function on the court.
Rondo will lose this struggle, inevitably. What Carlisle has built is too beautiful and effective to be torn down and refashioned to suit the predilections of a player who is noticeably no longer at the peak of his powers, and in the last year of his contract. This is not to say that Carlisle is the only party who would win through this outcome. Rondo needs to find a way to contribute without dominating, if he is to help the Mavs and also if he wants to make the next act of his career as successful as the last one.
This is easier said than done. Doing this will require Rondo to understand both himself and what he does on a basketball court differently. He must allow someone else's gravity to pull him along, for once. He has 23 games and two months to do this. Whether that's enough time to fully convert and adjust is probably beyond his control. All he can do is decide to try.