MIAMI — Their big early lead was gone, the Miami Heat were trailing with three minutes remaining and the two-time defending champions seemed very much in trouble Tuesday night.

They didn’t let Boston score again.

That’s how to snap a defensive slump.

LeBron James scored 11 of his 29 points in the fourth quarter, Chris Bosh added 16 and the Heat beat the Celtics 93-86, finishing the game on a 9-0 run after trailing 86-84 with 3:08 left.

“It’s difficult doing what we do,” Bosh said. “But that’s why we’re the champs, to do the difficult thing again and get the job done. Tonight was a good start. We just have to build off of it.”

Chris Andersen scored 13 points and made all five of his shots for Miami, which had given up at least 100 points in four of its last six games. The Heat are 25-1 when allowing fewer than 100 points, 5-11 otherwise.

Brandon Bass scored 15 points, Kris Humphries had 14 points and 13 rebounds, and Jeff Green had 12 points for the Celtics, who enjoyed a 46-33 edge in rebounds but shot only 39 percent.

And when it was over, Celtics Coach Brad Stevens had a simple assessment of the final three minutes.

“LeBron James happened,” Stevens said.

James made seven free throws in the final 2:33, the only other points down the stretch coming on a jumper by Ray Allen that put the Heat up for good. James did the rest while the Celtics missed their final four shots.

Rajon Rondo, still coming around after returning from knee surgery, missed all eight of his shots, plus a pair of free throws with the Celtics down four with 44.4 seconds remaining. Avery Bradley, the Celtics’ other starting guard, was lost in the second quarter with a sprained right ankle.

“LeBron got a bunch of calls down the stretch,” Bass said. “We expect that. We just wish we could have kept him off the line.”

The Celtics rallied from a 10-point deficit to win 111-110 in their first trip to Miami this season. They seemed poised for a bigger comeback this time, steadily chipping away at a big Miami lead by getting it down to 11 by halftime, then four entering the fourth.

And a dunk by Humphries with 3:08 left, about a half-minute after James tried a reverse dunk that rimmed out, put the Celtics on top for the first time since the opening minutes.

Thus ended Boston’s offense for the night.

“It’s the only way we’re going to be able to win games, if we defend,” James said.

As if playing without Dwyane Wade isn’t difficult enough for Miami — he was out for the 12th time this season — the Heat found themselves facing a sticky situation at his position just 1:11 after tip-off.

Allen, who started in Wade’s spot, was called for two fouls in 11 seconds. But the Heat left him in until 4.3 seconds remained in the opening quarter, a move that paid off two ways. One, Allen didn’t get in any deeper foul trouble. Two, Michael Beasley made those 4.3 ticks on the clock count.

Beasley banked in a 35-footer at the horn of the first quarter to give Miami a 29-15 edge. And another beat-the-clock 3, this one by Bosh with 2.0 seconds left and somewhat less dramatic than Beasley’s, put Miami up 51-40 at halftime.

Boston used a 13-2 run to get to 42-35 late in the second. That’s when Greg Oden made his first home impact with the Heat.

Odenm playing in Miami for the first time since Nov. 12, 2008, blocked a dunk attempt by Green, then after a timeout had a follow slam of a miss by James to help snuff out the Boston rally.

The Celtics just kept coming back. But the Heat had the final answer.

“(Miami Coach) Erik sits there and it’s been a long stretch for them, a hard stretch for them,” Stevens said of Spoelstra. “I’m sure the last five minutes he feels really good about what he can build on moving forward because that team’s really good and they didn’t even have Wade.”

NOTES: The Heat are 24-6 when Wade plays, 6-6 when he doesn’t. … Former Heat center Joel Anthony, traded to Boston last week, got a video tribute on the scoreboard and a standing ovation in the first quarter.