The deep scars from Allen's emotionally charged departure last summer from the team he won a championship with are gone. Any pain from petty rifts with any former teammates, many of whom he bonded with for five years, has vanished.
"I think I've moved on, but who I was as a Celtic will always be inside of me, as well as everything I played for," Allen said of his highly anticipated return to Boston, now as a member of the Miami Heat. "All of those memories my whole career, you look back at everything I've done, it's a collection of many different places and people."
So when Allen returns to Boston on Sunday for his first game since the breakup with the Celtics and joining the arch-enemy Heat in free agency, he's not certain what to expect.
Will Boston fans vehemently boo and jeer him for bolting to the team that ended their season each of the past two years? Or will they respectfully acknowledge his accomplishments there, where he became the NBA's career leader in 3-pointers alongside Paul Pierce, Kevin Garnett and Rajon Rondo on teams that twice reached the Finals?
"I'll deal with it when it comes," Allen said. "But you never really know until you get there."
After beating the Cavaliers in LeBron James' first trip back to Cleveland in 2010 and defeating the Raptors in Bosh's initial return to Toronto later that same season, the Heat want to keep the trend going for Allen, who still owns a home and bases his charitable efforts in New England.
"The biggest thing we can do for Ray is just to be prepared to win," said Heat guard Dwyane Wade. "Regardless of what he says or not, it's going to be a little weary for him. We're going to go out there and try to play our best game."
There was a mixed reaction to Allen when the Heat and Celtics met for the Oct. 30 season opener in Miami. Allen slapped fists with several Celtics players before the game, but never approached Rondo and was noticeably ignored by Garnett, who didn't acknowledge Allen's gesture and refused to look in his direction as Allen approached Boston's bench.
Allen had 19 points in 31 minutes during the Heat's 120-107 win. After the game, Allen greeted Celtics coach Doc Rivers and several players and coaches on the court.
But does he expect that same treatment Sunday in Boston?
"I never really have to think about that," Allen said of possibly approaching his former teammates and coaches before the game. "I just go out and do what I've always done and be who I've always been. I'll let whatever they feel come to fruition, but I'll treat it like any other game."
Despite every attempt to downplay his return as simply another business trip, Allen couldn't quite dodge the drama surrounding the showdown between the Heat and Celtics. His departure from Boston might not even make him the biggest villain in the building on Sunday afternoon.
Allen said Friday his feelings for Boston and Celtics fans haven't changed regardless of how they respond to him during the game.
"My sentiment doesn't change regardless of how they respond toward me," Allen said. "I have some great memories and played in some big games, won some big games. I'll always cherish those moments."
There's a good chance some of the Celtics and their fans might not forgive Allen for leaving town to take far less money and a shorter contract from the Heat. But they'll also likely never forget the epic performance James had in Game 6 of the conference finals at TD Garden last June that essentially snatched the series away from Celtics.
With the Heat trailing 3-2 and on the road facing elimination, James responded with arguably the best playoff game of his career with 45 points in 45 minutes along with 15 rebounds in the 98-79 win to even the series.
The Heat went on to win Game 7 in Miami and then trounced Oklahoma City in five games to win the title. But that Game 6 outcome in Boston proved to be a pivotal moment for both James and Allen, who reflected on that game this week and knew at the time that it might have been his last game in Boston as a member of the Celtics.
Boston reportedly offered Allen a two-year, $12 million deal after the season but also formulated an alternative plan to sign other free-agent shooting guards. Even before Allen made his decision, Boston had already agreed to a deal with veteran Jason Terry and would later add Courtney Lee.
Allen instead signed a one-year deal with the Heat worth about $3 million that includes a second year at his option. Allen has since admitted he didn't necessarily agree with the team's direction last season -- he lost his starting job to second-year guard Avery Bradley -- and also had a deteriorating relationship with Rondo and other teammates.
"I just knew that going into the summer, there were going to be some questions that had to be asked and answered by me internally ... and questions that I had for them as an organization moving forward," Allen said when asked at what point he figured his time was over in Boston. "I just knew I was moving into the summer a little differently than I had in summers past."
The transition hasn't been seamless for Allen or the Celtics.
Allen, 37, entered the weekend shooting 47.6 percent from the field and 43.9 percent from 3-point range this season -- both above his career averages. But while also averaging career lows in scoring (11.4) and minutes (25.6), Allen has repeatedly talked about his continued search for comfort and consistency in Miami as the full-time sixth man.
Meanwhile, Boston will enter Sunday's game eighth overall in the East and saddled with a losing record. The Celtics have struggled with injuries and disappointing stretches from key rotation players. Recent frustrations have led coach Doc Rivers to threaten through the media this week that players would be traded if their effort doesn't improve.
Allen said he's kept up with the Celtics only minimally this season and doubt they've tracked his progress in Miami.
"If they're on TV, I see it. But I don't seek it out," said Allen, who was then asked if he believed the Celtics might miss him, considering their struggles. "I couldn't tell you. I couldn't. There's so much that goes on media-wise up there. I guess we'll see when we get there."
If Allen really doesn't know what to expect, he could seek some reliable advice from his Heat teammates who have experienced similar returns to former stomping grounds.
The Heat and league hired extra security for the team when James played his first game back in Cleveland three years ago after leaving the Cavaliers in free agency. James was booed throughout the game and several fans were escorted from the arena, including some directly behind the Heat bench, for hurling items and using vulgar language toward James.
The scene was far less hostile but still intense when Bosh returned to Toronto after departing in free agency. After the game, Bosh bowed and sarcastically blew kisses to the same crowd that jeered him during the game.
Bosh anticipates Allen's reception will be a bit more like the one James got in Cleveland than his in Toronto. His logic stems from the notion that fans might be more upset at Allen because he won a title in Boston and was still part of a championship-caliber team before he joined a rival.
"That only makes it sting more -- that will ratchet it up more," Bosh said. "Who on this team has gotten cheers when they went back? Nobody. And I don't see it starting now. You were with them. But now, you're our guy. We know people are going to be on [Allen], so we just want to protect our brother out there and win it for him."
Allen won't be rattled by the moment -- or the memories.
"All positive," Allen said of his overall feelings about the Celtics and Boston. "Everything that I accomplished there, everything that I experienced there brought me to this place where I'm at now. And I'm appreciative of all of it, because the negative you learn from just the same."