MIAMI — MIAMI — Reserve guard Isaiah Thomas is listed at 5-foot-9 — and he’s probably smaller than that — but he was the biggest man on the court when the Boston Celtics needed him late.
Starting center Hassan Whiteside is 7-foot tall, but the Miami Heat center seemed small — and petty — when he hit Celtics counterpart Kelly Olynyk from behind and got himself ejected.
That was the long and the short of it on Monday night as the Celtics defeated the Heat 100-90 Monday night at AmericanAirlines Arena.
Thomas scored 12 of his team-high 25 points in the fourth quarter, playing through a bruised right elbow and a bruised back — two injuries he suffered when he took a hard foul from Heat guard Dwyane Wade late in the game.
“We tried to get him off the ball,” Celtics coach Brad Stevens said of Thomas, who is averaging 21.4 points in the 10 games since Boston acquired him from Phoenix, “and that was effective.”
Whiteside, who finished with seven points and nine rebounds, was tossed with 2:45 left in the third quarter.
It was the fourth consecutive game Whiteside played in which he was assessed a technical foul or disqualified from further competition. He was also ejected last week against Phoenix.
“We’ll handle it,” a clearly irritated Heat coach Erik Spoelstra said when asked about Whiteside. “It will be corrected.
“Everyone is responsible to the team. With your actions, there are consequences.”
With 26 seconds left, the referees also ejected Boston guard Evan Turner and Miami forward Henry Walker. There was nothing major between the two players, but referees told both coaches they wanted to make sure tempers did not escalate.
As for Olynyk, he said Whiteside blindsided him.
“I don’t know what happened,” Olynyk said. “I didn’t even know who hit me. I just got back up.”
Boston (26-36) won for the third time in four games. The Celtics trail the Charlotte Hornets and Indiana Pacers by two games in the battle for the final two playoff spots in the Eastern Conference.
“We’ve been behind (in the playoff race) all year,” Stevens said. “We have to play really well over the final 20 games to have a chance because the other teams are playing well, too.”
Besides Thomas, the Celtics got 14 points and nine rebounds from forward Brandon Bass, who was a team-best plus-20 while he was on the floor. He had 33 points and 26 rebounds in two days, counting his performance against Orlando on Sunday.
The Celtics also got 13 points from reserve forward Gigi Datome, matching his career high.
Miami, despite Wade’s game-high 34 points — including 15 in the fourth quarter — had its season-best three-game home win streak snapped. The Heat (28-35) trail the Hornets and Pacers by a half-game.
Heat forward Chris Bosh, who has not played since Feb. 11 due to blood clots in his lungs, was back at the arena for the first time since his diagnosis. He spoke to the media before the game and to the fans just before tipoff. He then sat on the Heat bench during the game.
“I’m a huge fan of positive thinking,” said Bosh, who is expected to resume basketball activities in September.
Bosh’s presence, however, failed to inspire Miami as Boston led early, taking a 24-19 lead after the first quarter and a 43-40 edge into the halftime break.
Boston closed the third quarter on a 14-6 run, taking a 73-64 lead into the fourth.
The Celtics shot 44.8 percent from the field for the game, while Miami finished at 42 percent.
Besides Wade, the Heat had three other double-figure scorers: forwards Michael Beasley (14 points) and Luol Deng (11) and guard Mario Chalmers (12).
But the Whiteside ejection seemed to kill Miami’s remaining fight.
“He’s going to have to learn the hard way — not doing it his way,” Wade said of Whiteside. “Hopefully, he changes his mentality.”
NOTES: Celtics G Avery Bradley (elbow) is out but may return Wednesday when Boston plays host to the Memphis Grizzlies. … Celtics coach Brad Stevens on his new point guard, 5-foot-9 Isaiah Thomas: “We’re not taller, but we’re a lot faster, a lot shiftier.”