BOSTON — Rajon Rondo got his pregame orders from Doc Rivers. The Celtics coach wanted his point guard to concentrate on scoring.
Rondo did that — and so much more.
He finished with 16 points, 14 assists and 11 rebounds, and Boston handed Miami its biggest loss of the season, pulling away with a dominant third quarter for a 91-72 win over the Heat on Sunday.
Rondo had eight assists in that period when the Celtics outscored the Heat 31-12, turning a 49-44 halftime lead into an 80-56 advantage. They stayed ahead by at least 19 the rest of the way for their fifth straight win.
He also had 10 points in the first quarter. Not bad for a sometimes shaky shooter who hadn’t scored more than seven points in any of his previous five games.
“We told Rondo that we needed him to be a scorer. Not a playmaker, a scorer,” Rivers said. “He set the tone at the beginning of the game by doing that and I thought that loosened it up for everybody.”
He reached the triple-double mark for the fifth time this season with 8 1/2 minutes to play. It was his 13th consecutive game with at least 10 assists and another outstanding performance in a marquee game on national television, a scenario in which he seems to thrive.
“Four or five guys came up to me today and told me to be aggressive and show them what a great point guard (I am),” Rondo said. “So I just try to go out there and be great.”
The Heat were far from that, making just 34.8 percent of their shots. And LeBron James failed to get an assist for just the second time in his career.
“We didn’t make any shots,” Miami coach Erik Spoelstra said. “You don’t get assists off of missed field goals.”
The loss continued a couple of disturbing trends for the Heat — seven losses in their last 10 road games and three consecutive setbacks of at least 15 points. Their previous worst defeat of the season came just one week earlier, 103-87 at Oklahoma City, and their last loss of more than 19 points came on March 4, 2011 at San Antonio, 125-95.
Miami has the fewest home losses in the league at 21-2 but is only 16-12 on the road.
“It’s definitely a string of issues on the road,” James said. “We’ve got to be more mentally tough.”
The Heat, playing their third game in four days, were led by James with 23 points and Dwyane Wade with 15. Chris Bosh, the other member of Miami’s “Big 3”, scored the Heat’s first four points but didn’t score again.
The Celtics, combining tenacious defense with outstanding play in transition, increased their Atlantic Division lead to one game over idle Philadelphia.
Paul Pierce scored 23 points, and Brandon Bass added 16 points and 10 rebounds for Boston.
“We know we can play with the best,” Pierce said. “It feels great. The crowd is behind you. You’re executing. You’re not turning the ball over. You’re rebounding. That’s the type of game we have to play.”
Does such a dominant performance against one of the NBA’s best teams boost the Celtics’ confidence?
“I don’t know if it does anything for our confidence,” Rivers said. “Our guys are a pretty confident group. They feel they can play with anyone.”
Miami scored two of the first three baskets of the third quarter, cutting the lead to 51-48. Then the Celtics outscored the Heat 29-8 the rest of the period, hitting 14 of 23 shots while Miami made only 5 of 19.
“The lead went from five to almost like 20 in the snap of a finger,” Wade said. “We got shots. We didn’t put them in and they capitalized on it.”
It was 55-50 when Rondo’s layup began a 17-2 run in which the Heat’s only points were two free throws by Wade. James finally hit a field goal, making it 72-54, but the Celtics scored eight of the remaining 10 points in the quarter.
And they kept up the defensive pressure in the fourth quarter.
“The game is a game of runs,” Rondo said, “and we know they’re a big team that can make a lot of runs, make like a 14-0 run. So we want to continue to get stops defensively and push the ball offensively up the court.”
The Celtics led 29-19 after one, led by Rondo’s 10 points, four rebounds and four assists. They stretched that to 34-23, then went cold offensively while the Heat scored the next 10 points, closing the gap to 34-33.
Bass stopped the drought with a shot from the top of the key with 4:57 left in the first half, Boston’s first points in 4:08.
With the score tied at 40, the Celtics got the next five points on a jumper by Kevin Garnett and a three-point play from Pierce to take a five-point lead.
Notes: Rondo’s streak of double-figure-assists games is the NBA’s longest since Steve Nash had 14 in March-April 2005. … Miami’s Udonis Haslem returned to the team after missing Friday night’s 113-101 win in Toronto, remaining in Florida to attend to a personal matter. … James scored in double figures for his 407th consecutive game. … Boston’s Ray Allen missed his sixth straight game with a sore right ankle. … Avery Bradley made a highlight-reel block on Wade in the second quarter that sent the Miami guard sprawling to the floor. “I patted him on the butt and told him he looked like me on that play,” Wade said.