Paul Pierce, Kevin Garnett and Ray Allen (l-r) are in their fifth season as the Boston Celtics' 'Big Three', but it could be their last one together. (AP)

The Miami Heat and the Boston Celtics are squaring off in the NBA’s Eastern Conference Finals. While Miami’s Big Three are trying to secure their place in NBA history with a title, Boston’s Big Three are attempting to add to their legacy in what could be their final season together.

In 2007 the Boston Celtics finished with a record of 24 and 58. It was their third losing season in four years and one of the worst in franchise history. But trades brought change in the form of two long-time NBA stars still seeking their first championship rings: Kevin Garnett & Ray Allen. And at their first Celtics press conference, team captain Paul Pierce welcomed the reinforcements.

“We’ve all been in the same situations,” Pierce said. “We’ve been on teams where we’ve had to carry a lot of the load for a number of years and as you all know, you can’t win that way.”

But with the new Big Three in place, the Celtics and head coach Doc Rivers did win. That season they earned the first Celtics championship since the large triumvirate of Larry Bird, Kevin McHale and Robert Parish roamed the parquet.

Doug Collins is the head coach of the Philadelphia 76ers and spent years covering the league as a broadcaster. He says not all NBA players would have been willing to share the spotlight.

“I remember talking to Doc Rivers about it when it happened and he said it was the right time for [Allen, Pierce and Garnett] to be able to do something like that because they had all been in the league long enough to sacrifice individual stuff for team stuff,” Collins said after facing the Celtics in the Eastern Conference Semifinals. “So my hat’s off to them. They’re wonderful people. They’re champions as athletes and they represent the NBA the way it should be represented.

In 2010, the Celtics returned to the finals, falling to the Los Angeles Lakers. And now they’re back in the Eastern Conference Finals for the third time in five years. But Garnett and Allen both become free agents at the end of the season. Allen turns 37 this summer. Garnett just turned 36. After the Celtics eliminated Atlanta from the playoffs last month, the famously intense Garnett reflected on what keeps him motivated.

“Not knowing if this is my last year to play … to come here every day is an easy thing to do.”

There are plenty of people in Boston who’d like to see Garnett stay. Outside the TD Garden, before Saturday’s Game 7 against Philadelphia, Sarah, a Concord, Massachusetts resident, who asked that we only use her first name, said she hopes the franchise can keep the Big Three intact.

“I’d be heartbroken. I would be. [There's] a lot of special meaning coming to the Garden watching them. I remember Larry Bird from when I was little, but I think this is the group I’m attached to.”

Nashua, New Hampshire resident Josh Boucher says regardless of how this season plays out, the 2008 championship provided his defining memory of the Celtics.

“I see that picture of Paul, Garnett, and Ray Allen together holding the trophy,” Boucher said. “That’s what I’ll picture for the rest of my life.”

Wednesday night in Game 2 of the conference finals against the Heat in Miami, point guard Rajon Rondo posted a career-high 44 points adding 10 assists and 8 rebounds. It was a performance that might one day be viewed as a symbolic passing of the torch, but the effort still fell short, with the Celtics losing in overtime. But last Saturday, Rondo’s triple-double did power the Celtics’ close-out win over the 76ers and Collins.

“I don’t look at them as the Big Three. I look at them as a ‘Championship Four,’” the coach said. “If you’re going to leave Rondo out, you’re making a huge mistake because that guy’s the motor that drives this team.”

Big Three? Big Four? Either way, Game 4 of the Eastern Conference Finals is Sunday night in Boston.