The two future Hall of Famers enjoyed so much success there, winning a championship in their first season together (2007-08). In their six seasons playing under coach Doc Rivers, Garnett and Pierce's Celtics won five Atlantic Division titles and advanced to two NBA Finals.
"Some things are forever, man," Garnett said Friday night. "And I'm happy to say that I'm part of that era."
Garnett and Pierce, who played the first 15 seasons of his career with the Celtics, were traded to the Brooklyn Nets during the offseason. They appear to have finally moved on and embraced their new opportunity, but they'll certainly never forget where they came from, where they cemented their legacies as two of the greatest players to ever wear the white-and-green uniforms.
"There's gonna be a lot of emotions," Pierce said. "You play your whole life there. You won a championship there. The first time coming there as a visitor, I never thought it would happen, but it is and it'll be here Sunday."
The Celtics, who are expected to honor the duo in grand fashion, had missed the playoffs in consecutive seasons and hadn't captured the title since 1985-86 before Garnett and Ray Allen arrived via trade, teaming up with Pierce to form the Big Three and lead Boston to an NBA title for the league-best 17th time in franchise history.
"I'm just fortunate to be part of that whole transformation," Garnett said. "Everything we put into those six years, everything we invested in them, I think the people from Boston, New England and Massachusetts, I think they understood that. They saw the hard work that we put into it, the effort more than anything.
"... Larry Bird said you can't fool the people of Boston. They know when you're working hard. They know pure basketball, and that's right. When you go all out they understand that, they root for that, and that's what they remember."
Added Garnett: We're going there with good thoughts and open arms. Boston was good to me. Boston was a whole-'nother episode for Paul because he's been there for the good and bad. All in all it was good times."
Pierce said he's already talked to (Celtics team equipment and travel manager) Johnny Joe, "And I told him I'll probably sit in the equipment room like I always used to. It's going to be a little weird.
"It's gonna be a fun time just going there and seeing some of the guys I played with, seeing some of the season-ticket holders, and some of the people that have been there, [TV broadcasters] Mike [Gorman], Tommy [Heinsohn]. It'll be fun to see those guys."
Garnett was asked about his favorite memories.
"The obvious ones. The winning stands out," he said. "The times where guys were beat up and played. I can remember Paul playing through the flu in Cleveland. He was throwing up and everybody saw him take like two or three IVs and he played. The times where Ray messed up his foot and played. [Rajon] Rondo gutting through his elbow [injury]. Big Baby [Glen Davis] damn-near having a concussion and coming back. Doc being sick in Detroit, gutting through it with a hoarse voice, he couldn't even talk.
"Small things like that I don't really want to share with you guys for obvious reasons. The ceiling in LA. ... You have no idea what the hell I'm talking about, but these are certain things that stand out to me that I'll never forget."
The Celtics decided to go into rebuilding mode during the summer, and found a willing trade partner in the Nets, who were looking to win now. Pierce had to convince Garnett not to retire and waive his no-trade clause and join Pierce in Brooklyn. Both players looked uncomfortable early on, struggling to adjust to being "glorified role players," and the injury-plagued Nets were 10-21 at the end of 2013. But they are 9-1 since the start of the new year, and the rejuvenated play of Garnett and Pierce is a huge reason why.
Garnett has made a huge impact since reluctantly moving to center in place of Brook Lopez, knocking down mid-range jumpers, rebounding at a high rate and anchoring the defense as a tenacious rim protector. Pierce has excelled since moving to power forward, and has proved to be a matchup nightmare for opposing teams.
"The difference in the way we're playing is we were thinking secondary as we came in," Garnett said. "And then Brook falls [and suffers a season-ending injury], Deron [Williams] has been beat up, we've had to be primaries now. And when you're a secondary, which is the first time in our careers, you take a step back. You're not as forceful. You don't want to step on everybody's toes. And when you're a primary plays are being called for you. Not only that, but you're touching the ball, you're in a rhythm.
"And then the mentality of a primary is different. We're thinking like primaries, we're out here trying to be aggressive. I think guys on the team are looking for us to be that. I don't know. I guess the mindset of coming here helping versus being [primaries], is just a difference. And we've come out with the competitive nature that people know us [for]. And we're not asking any questions and our team is looking for us to be that, to lead with that leadership, and that's the difference."
Garnett has embraced the opportunity to have Pierce as a teammate during their run together.
"To make this whole transition efficient and worthwhile, it's (been big) having someone that's your partner and your brother, someone who's been there with you," Garnett said of Pierce. "Someone I've recognized a lot of things with, a personal friend, a brother, to go through this whole process we're sort of exiting together -- me probably before him. But for the most part, to go through this whole thing not only with him but with Jet [Jason Terry] also, that's made it a little more easy."
Added Pierce: "We shared so many memories on and off the court. We shared our best memories in Boston. We won a championship and we talk about the ride together and the run. It's been fun just to be able to share it with him."