MIAMI – For six games and almost 40 minutes, the Celtics traded shots with the Heat. They took the best that LeBron James had to offer and countered with the combination of Rajon Rondo jabs and Kevin Garnett haymakers.

Back and forth they went from down 2-0 to a chance to close it out at the Garden – a chance that will live forever in infamy, as it turns out. Then, in the final round they went toe-to-toe one last time. There were 10 ties and 20 lead changes in Game 7 before LeBron finally landed the knockout.

You’ll have to forgive the boxing analogies, but that’s how the Celtics view themselves – as old prize fighters who refuse to stay down on the mat and who always think that the next time will be different. Give them this much: They went down swinging. But after Ray Allen popped in a 3 to give them a one-point lead, they were outscored, 20-6, over the final eight minutes and 49 seconds in a 101-88 loss.

“This one hit me hard,” Allen said as his steady emotions began to get the best of him. “We wanted it so bad.”

In the end it was their offense that betrayed them, as it has throughout the 2011-12 season. They had to work so hard to create space and they simply ran out of room. The Heat took away Kevin Garnett in the paint and they forced Rajon Rondo into playing a twisting, contortionist halfcourt game, rather than the chaotic end-to-end mess that is his true strength.

Allen and Paul Pierce tried to steady them with long-range bombs. Brandon Bass did his part, as well, but not even Rondo’s triple-double – 22 points, 10 rebounds and 14 assists could save them. The Celtics had only lost one other time when Rondo posted a triple double, but they had no answers for LeBron’s 31 points or Chris Bosh’s unexpected corner 3 attack.

“Honestly, I thought we had nothing left,” Doc Rivers said. “That’s how it felt as a coach. I was trying to push every button we possibly had. Everything was the front rim. We started throwing the ball away. They started beating us off the dribble.”

Without Jeff Green, Chris Wilcox and Avery Bradley, the Celtics took this as far as it could go and now they plunge headlong into an offseason of uncertainty. They’ve all known this was coming and they fought for as long as they could to delay the inevitable. Change is coming, however, and it will probably happen soon.

Almost all of the free agents said they wanted to come back from Keyon Dooling to Mickael Pietrus to Brandon Bass and there may be a place for them in the next era of Celtics’ basketball, provided the price is right for both sides. But for the Big Three, there is doubt.

Allen made it clear he intends to continue his career once he gets surgery to remove the bone spurs that plagued him throughout the postseason and forced him to alter his finely-honed mechanics. He made a great sacrifice playing through pain and coming to grips with an injury that probably would have sidelined him if he was in any other situation. But the future is changing and there’s real doubt whether there’s a place for Allen.

“There’s still a lot of basketball left in my legs,” Allen said. “I know that for sure. So it’s hard to say what can happen, what may happen. But [the] four of us know how to play basketball. We know how to win games.”

Perhaps even less clear is the future of Garnett. He left without talking to reporters, just as he did last season after the Celtics were eliminated in Miami. There’s no question they want him back, but there is some doubt as to whether Garnett himself wants to return anywhere.

He’s dropped hints throughout the season that this could be it for him. The lockout left a sour taste in his mouth and it’s doubtful that he’d want to be a part of a rebuilding process. Even as they try to get younger and more dynamic to keep pace with Rondo, there’s a place for Garnett. There’s always a place for Garnett.

“He has been everything with his locker room presence, desire, determination and leadership,” Pierce said. “He changed the culture of everything we did around here. He made everyone accountable. It would be great for me to end my career with Kevin. I have a couple of years left. Hopefully management can add a few pieces that we need to get over the hump. If not, it’s been a tremendous ride.”

In time we’ll be able to consider the last five years in full and what it meant to the Celtics’ franchise. They won 70 percent of their games, an NBA title and came within two Game 7’s on the road of accomplishing more. It was always a fragile collection of personalities and body parts, but through hard work and sacrifice, they made the first part work. They never had any answers for the bone spurs and knee ligaments. There never are.

“I wish we could have had healthy runs,” Rivers said. “This team won a title. Got to another one, a Game 7, where they had a shot to win. Got to the Eastern Conference finals and one game away on the road. Banged up. So, I don’t know – because of really Kevin’s injury [in 2009] – I don’t know if we could have gotten more out of this group. I would have loved to have seen this team in this whole stretch where Kevin was injury free.” 

We’ve been saying good-bye to them for the last three years, but they never wanted to leave and they always had something left. They did not go quietly and they did not go gently. They created an era when none existed and while it seems like just yesterday, five years is a long time in this league.

“I know everybody will look at the Big Three individually,” Rivers said. “Kevin, Paul and Ray. I’m never going to look at them individually. They all gave up plus-seven shots each. They gave up minutes. I asked them to play defense and move the ball and they all did it, and they’re willing to do it for the better of the team. So, I think that’s what we should focus on: how much they gave up to try and win. That’s what I’ll remember most about them.”

There was a curious mix of present and past tense in the thick, humid air of South Florida. The reality is no one really knows for sure what will happen this offseason or what the Celtics will look like next fall. They fought so hard to hang on to each other and what they were able to create together. In their fiercely competitive minds, it could go on forever. Just add another piece here or there and go after it one more time.

“We’ll find that out later,” Rivers said. “I just want to stick with this group. If it’s a couple more days, a couple more weeks, or whatever. I just want to stick with them.”