The Heat is in trouble now.

The last time LeBron James, Dwyane Wade and Chris Bosh fell behind 3-2 in a series, the Dallas Mavericks finished off the Heat in six games. The situation the Heat finds itself in now might be even more difficult to manage than last year’s NBA Finals.

Miami’s 94-90 loss to the Celtics on Tuesday at AmericanAirlines Arena sends the Heat back to Boston with no wiggle room in the Eastern Conference finals. Lose one more time — and the Heat has only won once in Beantown in the past two years — and it’s curtains for Pat Riley’s grand experiment.

LeBron James scored 30 points and had 13 rebounds in 45 minutes and Dwyane Wade bounced back from another sketchy first half to finish with 27 points but it wasn’t enough to counter another balanced scoring effort by the Celtics.

Five players scored in double figures for Boston. Kevin Garnett led the Celtics with 26 points and 11 rebounds. Rajon Rondo had seven points and 13 assists.

“We played hard but they made runs,” James said. “Every time they got down, they made runs.”

Historically, Game 5s have been precursors to crowning a series champion. The winners of Game 5s in best-of-7 series tied 2-2 have gone on to win the series 83 percent of the time.

The Heat outrebounded the Celtics 49-39 but couldn’t overcome a poor shooting night. Miami shot 39 percent from the field and 26.9 percent from three-point range. Wade had 14 points in the fourth quarter and James contributed nine, but the Celtics hung in thanks in large part to four three-pointers — two by Paul Pierce and two by Mickael Pietrus.

“OK, it’s a loss and that’s all it is,” Heat coach Erik Spoelstra said. “That’s all our focus is on right now — to fight any outside noise. This is the journey we have to be on for whatever reason. But it’s behind us now. Our energies have to be ready for [Game 6].”

Big shot

Pierce, a veteran superstar perhaps making his last push for another NBA title, knocked down the shot of night when he elevated in James’ face and drilled a three-pointer with 52.9 seconds left to give Boston a 90-86 lead. Pierce finished with 19 points on 6 of 19 shooting.

“He’s a big shot-maker,” Rivers said. “Always has been.”

Mario Chalmers missed a three-pointer with under 45 seconds to play and an out-of-bounds call was reversed in favor of the Celtics following the miss. After a miss by Rondo, Wade made a pair of free throws with 15.2 seconds left but Ray Allen answered with a pair of his own to keep the Celtics’ four-point cushion intact.

“I asked a lot of our guys, maybe too much at times, and they came through,” Celtics coach Doc River said.

After missing nine-consecutive games because of an abdominal strain, Bosh returned to action with nine points and seven rebounds off the bench in less than 15 minutes. He had a major impact in the first half— nine points and six rebounds in 10 minutes — but was limited in crunch time.

“There’s no reason to really dwell on it,” Bosh said. “We have to go to Boston and win. We’re in the biggest challenges of our professional careers. We have to win.”

Bosh finished with nine points and seven rebounds. Spoelstra chose not to play him in the final important minutes of the game, instead going with Udonis Haslem.