The Boston Celtics have never made it a habit to celebrate division titles. Not with Bill Russell blocking shots, or with John Havlicek, or with Larry Bird, and not with the new Big Three. The NBA’s winningest franchise only hangs banners for league championships, not for beating out the New York Knicks and Philadelphia 76ers in the Atlantic Division. Getting to Game 7 of the Finals and losing was a disappointment, just like losing in the second round was, just like anything short of hanging an 18th banner this season would be.

But this year’s Atlantic Division title, the team’s fifth straight, still carries more significance than the past four.

“I don’t know if I’ve ever congratulated the team for winning one,” Doc Rivers said. “But I did tell them, ‘Guys, I know it’s not a big deal to us’ — and it isn’t because we’re not in this to win divisions — ‘but we were two games under .500 at All-Star break and the fact that you did it and did it this early I think is very impressive.’”

The Celtics went from 15-17 at the All-Star break to 37-26 now, clinching the Atlantic Division with three games remaining on the schedule. They’ve lost Rajon Rondo and Ray Allen for significant time, and Jermaine O’Neal, Chris Wilcox and Jeff Green for the season (Green before he played a single game). They can’t rebound on most nights and can’t score on many others. They are aging and they are supposed to be past their collective prime.

But they’re proud.

“Don’t count us out,” Garnett said. “You guys called us old, over. I read some of your pathetic articles, some of your lousy analysis. It’s opinion and obviously you don’t know what drives us. We thank you for those articles and we appreciate it because it lit a fire under us.”

There were no champagne showers after the clinching win, there was no real celebration. Again, these Celtics are about more than division titles. It would be against their beliefs to celebrate something that to them is nothing more than a trivial paper accomplishment, which means nothing tangible except that it promises them at least the fourth seed. Yet even Paul Pierce, who noted that “all we care about around here is a championship banner,” understands that this year is different.

“I mean, it is a good accomplishment,” he said even after noting that he wouldn’t pop any bubbly. “The guys should recognize where we came from to what we are today.”

This season has been a process as the veterans worked themselves into shape, as a bench filled primarily with newcomers molded into a cohesive unit. Garnett complained that reporters and columnists counted the Celtics out, but it was their own doing. After getting ousted 4-1 by the Miami Heat in last year’s playoffs, the Celtics started 4-8 and then, after a brief revival seemed to right the ship, lost their final five games entering the All-Star break. Rivers and the players swore they found something they could build on during the final loss before the break, a 119-104 blowout to the Oklahoma City Thunder, but their words were difficult to believe. The Celtics, this proud, championship-driven team, taking moral victories from a 15-point loss? Oh, it seemed, how the mighty had fallen.

Except the Celtics made good on their word. The team that returned after All-Star break was different. It helped that Garnett started playing center, Avery Bradley began proving himself, Rajon Rondo took off chasing after John Stockton’s double-digit assists streak record and Paul Pierce steadily managed to provide whatever the Celtics needed, but the success was marked mostly by a team-wide commitment to, well, the team.

“They just kind of figure it out,” Rivers said after last night’s 102-98 win, and it was far from the first time he praised the team’s mental makeup.

Against the Magic, Pierce took over Rondo’s role of distributor and dished 14 assists. Bradley continued to occupy Allen’s former role of starting shooting guard and poured in 23 points. Greg Stiemsma blocked four shots and protected the interior after Boston had been weak there to begin the night. E’Twaun Moore played legitimate minutes for the first time in what seemed like forever and drilled two important shots.

It was a prime example of what this team has become — a cohesive crew that thrives by giving whatever the game needs.

“One of the hardest things to do in this league is to create chemistry,” Garnett said. “I knew at some point as a unit we’d get a rhythm and ride that rhythm out. That’s what you’ve seen since the All-Star break. We came back refreshed, focused. Like I said, we don’t have a lot of practice time to implement our system, our schemes. But we do have a core here. What you’ve seen up until this point, obviously to a point where we’ve won the division, is not only confidence but believing in that system, believing in that rhythm and riding that rhythm out.”

These Celtics are your Atlantic Division champions. Whether they want to show it or not, they take some pride in that fact.  For the past four years the division title has been almost a given. But this season, the Celtics worked damn hard to get here.