When it comes to the Heat, it doesn’t take much for Miami’s legion of skeptics to seize on every mistake, miss or misstep. Doubt creeps in, then cascades over this team for which it’s all or nothing.

Back home Tuesday after an 0-2 road trip in Boston, Heat coach Erik Spoelstra challenged his players not only to win the basketball game but also to win the mind game. To assert their will. To be tougher, burn hotter, want more. To match the intensity of the savvy Celtics, and turn it up a notch.

But the Heat could not do it.

Miami bared its vulnerability, again. Miami had its chances but could not capitalize, again.

The Heat blew its precious home-court advantage in a 94-90 Game 5 loss to fall behind 3-2 in the seven-game series.

The questions about the lack of clutch plays and players will come thundering down on Heat heads, just as they did last season. Whether Miami can ignore the questions and withering criticism as it prepares for Game 6 will be key in determining whether they can win Game 6 on Thursday in Boston’s extremely inhospitable GAH-den.

Miami squandered a comfortable lead inside AmericanAirlines Arena, which went from boisterous to stunned. Then, it allowed the score to ricochet back and forth in the fourth quarter. Big breakdowns followed big shots for both teams.

Yet when push came to shove as it so often has in this “good ol’ bar fight” of a series, as Paul Pierce described it, the Celtics had the last punch. The Heat whiffed.

It was another entertaining, excruciating game. Fans’ nerves are frayed. Players’ legs are heavy. Coaches’ brains are fried.

But this rivalry between the aging Big 3 of Boston and the dynamic Big 3 of Miami keeps on delivering irresistible drama.

It was closer than it should have been for the Heat, and then it was a loss it could not afford.

Now the Heat faces “a test of character,” as Spoelstra put it. “That’s what the playoffs are all about.”

The Heat is 0-7 in these playoffs on game-winning or game-tying shots in the last 24 seconds of games. It has had to work frantically to dig out of 15-, 18- and 24-point holes in Games 2, 3 and 4, and lost two of those. Game 5 was different, at least for a while, because it was the Heat with the double-digit lead. By the time it got down to the last 9.4 seconds, the Heat was two points behind. Miami couldn’t finish.

One of the Tuesday headlines in Boston — above a photo of James — asked “Worried?”

Yes.

The pivotal shot Tuesday came from Pierce. He played chicken with LeBron James. He dribbled inch by inch closer to the three-point line as James crouched, ready to pounce. Then Pierce made his move, bounced off his feet and swished a three-pointer over James’ outstretched hand for a 90-86 lead with less than a minute to go.

“We had an opportunity to come home and take the lead,” James said. “We have to go to Boston and take one. There’s no other way out.”

James drove right past Rajon Rondo and soared by Kevin Garnett to give Miami hope with his layup with 9.4 seconds left.

But Garnett, fouled by Udonis Haslem, nudged Boston’s lead back to four with two free throws — extending Boston’s free-throw accuracy to nine in a row and 81 percent for the game.

Wade missed a long three-pointer and the game was over. The series? Miami is now the underdog and must win Thursday to bring it back to Miami for a Saturday finale.

The NBA playoffs can turn on a dime. Witness Oklahoma City’s three consecutive wins over the previously invincible San Antonio Spurs.

Boston got critical plays from Garnett, Pierce, Rondo, even Mickael Pietrus. Garnett blocked a shot by James. Rondo tipped a miss to Pietrus for a three-pointer.

“I take a lot of pride,” Garnett said. And, when asked about his reaction to Pierce’s three-pointer, he said, “Oh, God, the truth.”

Garnett scored 26 points, grabbed 11 rebounds, blocked two shots and altered many others. He looked to be in his scowling, sweating prime.

“He’s our life,” Boston coach Doc Rivers said. “He’s in a strange way a calming effect on some of our guys, if you can ever call Kevin that.”

One good thing for Miami: When Chris Bosh returned after three weeks with a strained abdominal muscle, he got a standing ovation. He sank his second shot, a sweet left-handed turnaround, and the cheers shook the arena.

Feeding the ball to James was the most reliable strategy. As in the third quarter when James cut under the basket, then rebounded his own miss for a put-back.

But most of the second half was an anatomy of a collapse.

In the first half Heat dazed Boston early by blazing to a 13-point lead while holding the Celtics to 30 percent shooting and 16 points in the first quarter. But as the second quarter wore on, the Heat inexplicably eased off the accelerator, the Celtics closed the rebounding gap, and by halftime, the Heat’s lead was a negligible two points.

Wade had another slow start, going 3 for 9, while James was unstoppable with 18 points and nine rebounds. Bosh gave the Heat a boost by scoring nine points in 10 minutes with six rebounds in the half.

“This is the journey we are on, for whatever reason,” Spoelstra said.

Rivers was more blunt: “We told our guys, just hang in there, don’t overreact. I think I asked a lot of our guys, maybe too much at times, and they came through and that was terrific.”

It’s going to take an incredible effort to pull this one out — just the kind of effort that will silence the questions and erase the doubts. If the Heat can’t come back and beat Boston, it will never hear the end of it.