One loss. That’s all it took for Doc Rivers to think to himself, “You know what? I need to define everybody’s role. We can’t fall into the same pattern we did last year.”

After the Celtics loss to Cleveland, Doc called a team meeting. In it, he talked to each player and told him what he thought his role should be. (Rajon, you run the team, but please stop throwing TOs. … Garnett, you lead us defensively, and for God’s sake be more aggressive with the ball. … Jermaine, umm, play better?) A genius move, no? Stop the problems early, before they escalate. Point out everybody’s roles before players try to do things they aren’t capable of — or, maybe worse, fail to do things they are capable of. You know Big Baby was happy — Doc finally explained his role.

“Everything [Doc] said was correct,” Shaq said.

And then, a couple hours later, Von Wafer and Delonte West brawled. In the words of Lebron James, Rome wasn’t built in a day. Maybe Doc should have defined what their roles should be in three-on-three games, too.

Despite the fight that followed shortly after Doc’s speech, what we know about the speech is encouraging. I spent half of last season screaming at my TV for Paul Pierce to rebound the basketball, then Doc addressed Pierce’s rebounding in yesterday’s rendezvous, then Pierce went out and pulled down 14 rebounds. Do you know how many times he grabbed 14 rebounds in a single regular season game last season? None. Do you know how many times he even snagged double digit rebounds? Once, and it was on opening night (11 boards). Thank you, Doc’s talk. You finally got Pierce’s ass into rebounding gear.

We know little else about the substance of Rivers’s speech, except that he told Shaq that the Big Fella needs to work on pick-and-roll defense. Maybe Rivers shouldn’t have wasted his breath on that point, but the fact of the matter remains: the meeting was productive. Rivers told his players what they needed to hear, not what they wanted to hear. He encouraged them not to fall into last season’s rut, and he did it at the first sign of trouble. The meeting was a sign that this year is different from last, that the Celtics (perhaps) now value the regular season.

Rivers must have felt like we did after the Cleveland loss. He didn’t want to overreact to one game, but that one game was haunted by the ghosts of last year. And you know what? His chat worked, at least for one day.

The Celtics started the game with zero energy (apparently, they used up a lot of their fight before the game), but from the second quarter on played hard. They didn’t execute perfectly, not by any means, and throwing the ball to the wrong team continues to be in style, but the Celtics earned almost every loose ball. They outrebounded the Knicks by 16 (which, granted, they’re supposed to do), but you don’t win the rebounding battle by that much unless you’re getting after it. And the Celtics were getting after it. They wanted last night’s win. Badly.

And though it wasn’t always pretty, they earned it. With an assist to Doc’s pregame chat.