The Heat may have won a regular-season game in the Garden for the first time in almost six years, but the Kevin Garnett-less Celtics sent a message on Monday night: Nobody in Boston is scared of the Heat. And Jeff Green of all people said it loudest.

“It was the best team in the league, and we took them to their breaking point,” said Green, whose career-high 43 points nearly dethroned LeBron James for a night. “When Kevin comes back, we’ve got to continue to play like we did today. With the addition of him, I think we will be more lethal.”

Nobody saw Green’s performance coming. Nobody but Danny Ainge and Doc Rivers.

“There will be nights when he has an advantage, and there will be nights when he will not,” the Celtics coach said after his team’s 105-103 loss. “We thought going into the game he would have that advantage, and we took advantage of it.”

This is why the C’s swapped Kendrick Perkins for Green in the first place. But he never acclimated down the stretch in 2011, and then heart surgery erased the following season. Now, for the first time in Boston, his approach has aligned with that of his coach and veteran teammates: He can play with the Heat.

“I believed we were going to win before the game,” said Rivers. “I thought we were going to win during the game. And I thought we should have won the game.”

The combination of Green and Paul Pierce gave Miami fits. James can only guard one, and that forced Heat coach Erik Spoelstra to counter with Udonis Haslem, a 34-year-old Shane Battier and -- for some reason -- Chris Andersen. While Battier made a spectacular block on a potential game-tying drive, that’s a matchup the Celtics can exploit. And those are few and far between against the Heat.

Considering the defending NBA champs arrived tied for the league’s second-longest win streak ever, the Celtics hosted without four of their best eight players to start the season -- Rajon Rondo (knee), Jared Sullinger (back), Leandro Barbosa (knee) and KG (groin, flu) -- and the result was a two-point loss, Rivers has to feel good about a potential playoff matchup with a healthy Garnett in the fold.

“That was our first playoff game for a lot of the new guys, and I was really looking forward to the game, because I didn’t know how a lot of guys were going to react,” Rivers said. “Overall, besides not winning the game, we passed the test.”

Of course, Rivers went just eight deep, playing only “new guy” Jordan Crawford, who somehow contributed almost seven minutes in the fourth quarter. Including KG, for better or worse, this is the C’s rotation -- lack of depth be damned. Still, absent their best matchup problem in Rondo, their small lineup (Avery Bradley, Courtney Lee, Pierce, Green, Garnett) presents a challenge for Miami, and the Heat seemed to sense that in the locker room afterward.

“It’s a Celtics-Heat game,” said Wade, who scored 16 points in a dogfight against the pitbulls over 36 minutes. “It’s always like that. Whether it’s the first game of the year or the last game of the year, it’s always like that. No matter who’s on the court, no matter who’s playing, it’s going to be a battle.”

Even without Rondo? Without Garnett? That’s saying an awful lot.

“We know we’re getting the best from Boston every time we play them,” added Wade. “There’s a dislike there. It’s a different focus, especially here in this building.”

Yet, Ray Allen acted (emphasis on acting) as if C’s-Heat isn’t the best conference rivalry going. “When I played here, our rivals were the Lakers, Pistons and New York,” he said. “That’s deep-seeded. It comes from a lot of basketball, and we’ll see how the years go to determine if that’s the case.”

A lot of basketball? The Celtics and Heat have played 20 times since James took his talents to South Beach. Each side has won 10. And the C’s history with LeBron runs deeper. Either James or the Celtics have been in all but one of the past five NBA finals, and they went through each other all four times. Allen should know better than anybody, since he’s now seen the antagonism from both sides.

“Nobody pulled punches for me today,” said Allen, who didn’t have any video tributes welcoming him back to Boston this time around. “I heard some pretty brutal things in the building today, and people really let me know how they felt. I don’t go into it with any expectation, but I’m on the other team, so they’re going to say whatever they can and whatever they think they need to say.”

If Miami fears anybody, it’s the Celtics. Sans Rondo, sans Garnett, they gave the Heat all they could handle. James has won five consecutive Player of the Month awards and 23 straight games, but as long as Pierce, KG and now Green are in Boston, they won’t back down. And that seems to bother LeBron.

Asked how the Celtics always seem to give the Heat a battle, James took offense. “Why does it always have to be that way?” he said. “Why does it always have to be, ‘They gave us a war’? There’s never us giving anybody else a war, huh? That's how y'all like it?”

Maybe James hasn’t seen his Chosen One tattoo or watched ESPN recently. He’s unquestionably the best basketball player on the planet, and he formed a super team with two other All-Stars in their prime, won the title and then convinced the game’s greatest shooter to bolt from Boston and join forces for half the price.

The Heat aren’t supposed to give anybody a war. They’re supposed to slaughter these old, injured and tired C's, leaving a blood bath in their trail.

Yet, here are the Celtics, rising from the dead.

"They're a good basketball team," said Miami's Chris Bosh. "Never count them out. Everyone counted them out last year, and they were one win from the finals."

On D&C Tuesday morning, Rivers fielded questions about a potential third straight playoff meeting between the two teams. “We’d enjoy that matchup," he said. "There’s no doubt about that.” Whichever round it may be, another Celtics-Heat series seems inevitable at this point, and that doesn't scare ayone in Boston.