Five years ago, Kevin Garnett, Ray Allen and Paul Pierce came together to salvage a franchise and complete their legacies as players. They accomplished both goals, establishing a new Celtics era on an identity that was forged on defense, toughness and a stubborn unwillingness to go gently into that good night.

Together they won almost 70 percent of their regular-season games, 11 playoff series, five division titles, two Eastern Conference championships and one NBA crown. In the wake of their success, Garnett was fully accepted into the all-time pantheon, Allen was recognized as perhaps the greatest shooter of all-time, and Pierce finally got his due as one of the game’s greats. Their individual talents blended so seamlessly into a coherent whole that it made you wonder why they had ever been apart for so long.

That’s gone now. Allen is in Miami and the Celtics will be a much different team this season. The offseason goal was to get younger, more athletic and more versatile. While the C’s still are built around Garnett, Pierce and Rajon Rondo, team president Danny Ainge drafted, signed or traded for 10 new players whose task is not simply to provide support for the revamped Big Three, but also to offer alternative solutions.

“I think the things you’re going to see out of some of the players on our team won’t be shocking but will be things you probably haven’t seen for quite some time,” Garnett said. “Different players in here bring different elements and it’s a good thing. It’s not just an onus on two or three guys. We have a real balanced team in here.”

There will be different lineups and funky combinations. They will be able to play big or small. They will be faster and less reliant on old legs. They will, if things go as planned, be able to create matchups on a nightly basis and dictate pace. It also will take time.

“I like the team,” coach Doc Rivers said. “I think we’ll have to be a better defensive team consistently to be a great team and I think there’s a lot of growth in our team. How fast we do it, who knows? We’ll figure that out as the season goes on. But if we do grow and all the different ways we can play and everyone gets it, I think we can be very, very good.

GOING GREEN

One day after practice, Jeff Green was holding court with the press, which in and of itself was something of a revelation. When Green first arrived from Oklahoma City he seemed overwhelmed with his new surroundings. He not only was joining a team that was set in its ways, he also was dealing with a crush of media that wanted his time on a nightly basis. It was, ultimately, an adjustment.

“I came into a situation where the team was already solid,” Green said. “They’d been together for years, so it was tough to come in and just try to pick my spot and where I was supposed to be and know my role. It takes time to do that when you come into an organization like this and with players like Kevin Garnett, Paul Pierce and Rajon.”

Someone asked him why he decided to hang around last season after undergoing heart surgery. Green stood up and pointed to the practice court.

“That guy right there. Rajon. I wanted to play with him,” Green said. “He’s the best point guard in the league. Who doesn’t want to play with a good point guard?”

If Green is more comfortable, Rondo finally seems at peace with his place in the team’s hierarchy. For the first time in years there were no trade rumors following him around the offseason. Allen, the cause of some tension, is gone, but Pierce and Garnett also are more at ease with Rondo’s role in their on-court success. Additionally, Rondo and Rivers have formed a true partnership.

This season, more than any other, will come down to Rondo. He proved in the conference finals that he’s capable of playing at a superstar level on a nightly basis under the most claustrophobic scrutiny and pressure. He’s also one of a handful of talents in the entire league that can slow Miami’s ascent. The Heat still don’t have a good answer for Rondo, and make no mistake, the Celtics are playing this season with one thing in mind: beating the Heat when it counts.

To further that cause, Ainge brought back Green and acquired Courtney Lee. Those two should finally provide the long-sought running mates for Rondo in the open court. Jason Terry fills the most pressing need as a shot-creator and scorer off the bench. Veterans Leandro Barbosa, Darko Milicic and Jason Collins are around for support. The Celtics have loaded up in the offseason before, but Ainge has never overhauled the roster the way he did this past summer.

Green is the key to the C’s newfound versatility. He’ll play everywhere but point guard and defend everyone in between. When Miami went small with LeBron James and Chris Bosh up front, the Celtics had difficulty matching up with all those perimeter options. Green is meant to be an equalizer.

“He’s the main guy when you talk about small lineups,” Rondo said. “He played the 4 at Oklahoma City. He stretched the floor with his shooting. We can get a lot of bigs on the floor as well. He can go from the 4 to the 3. Defensively, he can check 1 through 4, I believe. We expect a lot out of Jeff, but he’s fine with that pressure.”

In many ways, Rondo and Green are as much a link to the future as they are to the present, and by 2014-15 they will be the two highest-paid players on the team. But this is about now.

“This is the best team we’ve had since I’ve been here, I think, as far as on paper, as far as the depth of talent,” Rondo said. “We’ve got to make something of it.”

ROOKIE REINFORCEMENT

The overhaul began in late June with a bit of Auerbachian luck. Austin Rivers picked up on it right away. He turned to his dad and said, “Jared Sullinger’s going to fall to you guys. This is unbelievable.”

“He was shocked by that,” Doc Rivers said. Then the coach added, “I think Danny started that rumor.”

It was a joke, of course, but for all the moves Ainge made in the offseason, none were as fortunate as draft night when Sullinger fell out of the lottery and landed in the Celtics’ laps with the 21st pick. There were questions about his back and his overall conditioning. Those rumors picked up steam heading into the draft, and it was a very good thing for the Celtics.

The 20-year-old wasted little establishing himself as one of the league’s top rookies during two tours of summer league before suddenly finding himself with a very big role on a team that’s notoriously distrustful of young players. Yet the C’s have accepted him so quickly that it’s almost as if he’d been here for years. Sullinger is an old basketball soul with an old-school game that can help shore up two of the team’s biggest weaknesses: interior scoring and rebounding.

“He’s probably the smartest rookie we’ve had since I’ve been here,” Rondo said. “He’s very intelligent. High basketball IQ and he’s very unselfish. He doesn’t need a play called for him. He’s been getting his points off the dirty work.”

Sullinger’s emergence creates an interesting frontcourt mix for Rivers to work with. Brandon Bass was the only legitimate option next to Garnett last season, but now he’s joined by Sullinger, Green, Milicic and Collins. Suddenly, there are choices.

Whether Sullinger starts or comes off the bench is ultimately beside the point. He has forced his way into the rotation and he will play. And he comes equipped with a ready-made chip on his shoulder, which should be a prerequisite for playing with the Celtics.

“Six months into the college season he’s a top three pick, and then he goes 21,” Rivers said. “I wouldn’t be very happy with it. But listen, he has to do it for 15 years to prove them wrong. Not just one year. That’s the way he has to do it.”

“I could [not] care less about those GMs at this point,” Sullinger said. “There’s only one GM I’m worried about and that’s the man upstairs [Ainge]. He gave me an opportunity to play here, so I’m just going to live it to the fullest.”

You might think all of these new players would give Rivers pause. Sure, he loves the depth, but there’s only so many minutes and so many shots to go around. How will he keep everyone happy? Rivers is unconcerned.

“It doesn’t matter what they did in other places, it’s how they act with each other, when things are good and bad, when you play five minutes and 35 minutes,” Rivers said. “So all that plays out during the year. I don’t think we know our team yet. We know we have a chance to be really good. That sounds good. You have to actually do it.”

UNFINISHED BUSINESS

The chants started late in the fourth quarter, long after it had all been decided and they had blown it in excruciating fashion. They continued through the extended garbage time while the starters sat on the bench, fully aware that they had suffered one of their most devastating losses.

Let’s go Celtics

They had a 3-2 lead and a chance to close out the Heat on their home floor. It was all they could have asked for and certainly more than they could have expected way back in February when they staggered into the All-Star break with a losing record and a damaged psyche.

Let’s go Celtics

The Garden crowd always had been behind them, but this was something different. At the time, many chalked it up to a farewell tribute to an aging group of players who had given their best only to find out that it wasn’t quite good enough.

It was, however, something more than that. For half a decade the city of Boston slowly has warmed to these fascinating individuals. They were lionized as winners right off the bat, but that was to be expected. It took all the near-misses, the trade rumors, the injuries and all the failed experiments to fully understand what was happening. Through it all, they kept coming back again and again until finally they had become Boston’s team.

Once mysterious and almost unapproachable, Garnett has opened up and become part of the family. He’s your crazy uncle Kevin who always has a story to tell and wisdom to impart. The enigmatic Rondo no longer is the tempestuous younger brother. He’s a leader now, maybe the leader, although time ultimately will tell. As for Pierce, every day on the calendar becomes another day closer to the time when his number is raised to the rafters.

Five years feels like forever in the NBA, but as it turned out, it wasn’t enough time. Some teams refuse to lose. The Celtics refuse to die. They have unfinished business and a promise to keep to each other, their new teammates and the city that is ready to embrace them as never before.