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Lynne Sladky, Associated Press
Guard Ray Allen responds to a question during a news conference after signing an NBA basketball contract with the Miami Heat, Wednesday, July 11, 2012, in Miami.

MIAMI — Ray Allen could have easily taken the comfortable approach and stayed in Boston. He loves the Celtics' fan base. Teammates such as Kevin Garnett and Paul Pierce wanted him with them for another championship push. The doctors who have spent four years caring for his diabetic son are nearby.

All compelling reasons.

Just not compelling enough to turn down the Miami Heat.

The NBA's career leader in 3-pointers needs new cufflinks. He wore a diamond-crusted pair on Wednesday, the No. 20 surrounded by a circle. It was a nod to what is now his past, since 20 isn't his jersey number anymore. With the Heat, he'll wear No. 34 — his former number, the one that wasn't available in Boston because it belongs to Pierce.

"The last few days have been, I'd say, interesting," Allen said in an interview outside the Miami locker room, a couple hours after he sat next to Heat President Pat Riley and signed a contract with the reigning NBA champions that will pay him just over $3 million for this season. "They've been emotional."

He signed his deal on the same day that his close friend and former Seattle teammate Rashard Lewis also joined the Heat. He knows Dwyane Wade partly from their time in Milwaukee together — Wade was at Marquette when Allen was with the Bucks, and the two exchanged pleasantries for a few minutes when they crossed paths in the arena on Wednesday.

But Allen doesn't have many close relationships with Heat players. He did with many occupants of the Celtics locker room. And he is in Miami now anyway.

"When I made the decision, I had to say, 'Well, I know who's in my locker room now in Boston.' And the devil you know is sometimes better than the devil you don't know," Allen said. "So it is a leap of faith. And when you look at the guys, you say 'Hey, sometimes you do have to put changes into play and figure out how to make it work.'"

On the surface, the notion of making it work would seem simple. One of the best shooters in NBA history — more 3-pointers than anyone, a career 89 percent success rate from the foul line, 24th on the league's scoring charts with a legitimate chance of cracking the top 20 next season — just got added to a championship team featuring LeBron James, Chris Bosh and Wade.

Ultimately, the task of putting together the plan falls to Heat coach Erik Spoelstra, who seemed to hit it off with Allen when they spent hours talking philosophy of the game during a recruiting session last week.

"There's only a handful of players, really, in this league that absolutely strike fear into their opponent," Spoelstra said. "And Ray is one of those players."

Spoelstra and Allen apparently ducked out of a lunch with Riley and other Heat officials last week and chatted about all sorts of scenarios.

"I said, 'Where were they?' They were gone for two hours," Riley said in an effort to get to know each other better.

Whatever Spoelstra said must have helped, because a day later, Allen called the Heat and said he would accept their offer.

"Not every player is a great fit here," Spoelstra said. "We know that going into the process. But there are some that we immediately know, and without even talking to them, that we know they would be a great fit. And then when we had the opportunity last week to spend the whole day and evening with Ray, we knew this was everything we had heard about but more. We anticipate it will be a very seamless fit."

The same, everyone hopes, can be said for Walker Allen.

He was diagnosed with type-1 diabetes during the 2008 NBA Finals, just a few days before Boston won its 17th championship. Ray Allen has developed close relationships with several top doctors in the Boston area since, and his mother — Flo Allen, a courtside regular to cheer on her son — has run the Boston Marathon three times in an effort to raise awareness for diabetes research.

His son's care was a huge part of the decision on whether to sign with Miami. Even before the deal got done, plans were already being put in place to make sure Walker Allen would have all the support he would need in South Florida.

"We're saying goodbye to a lot of people that we grew up to know and love in our community, in the organization," Allen said. "Everything changes. You are sad about that. But it doesn't keep those people from still being close to our heart or still being friends."

The Celtics and Heat have forged quite a rivalry over the past three years. Boston ousted Miami from the playoffs in 2010, prompting Wade to vow that big changes were coming to the Heat. (They got James and Bosh a couple months later.) Miami beat Boston in the second round of the 2011 playoffs, then needed seven games to win a classic matchup this past season in the Eastern Conference finals.

Allen cried after the Game 7 loss this season. He also left with even more respect for Miami.

"I talk about playing the right way all the time," Allen said. "I've played this team quite a bit the last couple years and what I've always seen is them attacking and playing the right way, playing hard. They've built a great unit together as a group, so that to me comes from up above. It's a discipline-type attitude that the guys have and it starts from above and everybody follows suit and everybody's on board with it. And that's what you want to be a part of."

Still, he spoke with reverence about the way Celtics fans treated him for five years.

"To me, they'll always be the ideal fan base," Allen said. "I'll forever be indebted to them. Fans always have to represent their cities, because the players come and go, retire. We call home wherever we end up. But that's always their home. We get a chance to borrow it a little bit, represent it and try to do great things."

Now he'll try to do the same in Miami.

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