Miami ? With the outcome decided in the final seconds, LeBron James walked toward Mario Chalmers to begin his version of a celebration.

He playfully punched his teammate twice in the chest.

Fitting, because James and the Miami Heat have now landed two blows against the Boston Celtics.

James scored 24 of his 35 points in the second half, Dwyane Wade added 28 and the Heat used a late 14-0 run to pull away and beat the aching Celtics, 102-91, in Game 2 of their Eastern Conference semifinal series on Tuesday night.

“Feel good about it,” James said. “Series is far — far, far, far — away from over. It’s really just beginning for us.”

James shot 14-of-25 from the field, and logged 44 minutes with no turnovers. Chris Bosh finished with 17 points and 11 rebounds for Miami, which leads the best-of-seven, 2-0.

Game 3 in Boston isn’t until Saturday night, and the Celtics may be particularly thankful for the break.

Rajon Rondo played through a balky back to score 20 points and add 12 assists for Boston, which got 16 points from Kevin Garnett and 13 from Paul Pierce — who retreated to the locker room for treatment on his strained left Achilles’ in the first half. Ray Allen was held to seven points, and left with what he said was a bruised chest cavity courtesy of an elbow from James in the third quarter.

“Being down 2-0 doesn’t scare any of us, doesn’t make us nervous,” Allen said. “It’s just an opportunity to come out shining.”

Boston tied the game at 80 on a pair of free throws by Pierce with 7:10 left. The Celtics missed their next six shots and Miami pulled away, taking command of both the game and the series.

“That’s our staple. We know the only way for us to win games, especially in the playoffs, is to play defense,” James said. “Everyone has each other’s back. If one guy gets beat, another steps up. They made a run, a heck of a run … but we just kept grinding, kept playing our principles, and we finally wore them down.”

Even for a franchise with such fabled history as the Celtics, an 0-2 deficit represents a colossal challenge.

This is now the ninth time Boston has dropped the first two games in a best-of-seven series. In the previous eight, the Celtics prevailed only against the Los Angeles Lakers in the 1969 NBA finals.

And it’s something this group of Celtics has never faced before, either.

The last time Boston lost the first two games of a playoff matchup was in 2004, when it was swept by Indiana. The current core of Celtics had lost Game 1s four other times before this series, then bounced back to win Game 2 each time, against Chicago and Orlando in 2009, then Cleveland and the Lakers in 2010.

Not this time.

“Nothing we can do about it,” Celtics coach Doc Rivers said. “We’ve got a third game and we’ve got to take care of that.”