BOSTON -- Wednesday night was going to be special for Kelly Olynyk regardless of what happened in the game against his old team.

It turned out to be a night he will never forget.

"It was an emotional night, a fun night. I'm glad we came away with the win," Olynyk said after scoring a career-high 32 points to lead his undermanned Miami Heat to a stunning 90-89 upset of the Boston Celtics -- a game finally decided when Kyrie Irving missed an open 20-foot jumper at the buzzer.

Olynyk, who had 25 points in the second half, played the first four years of his NBA career with the Celtics before signing a four-year, $50 million contract with the Heat. He played in the Nov. 22 game in Miami where the Heat ended Boston's 16-game winning streak, but this was the homecoming.

He received an ovation during pregame introductions Wednesday and was honored by the Celtics with an award for charity work in the second quarter, producing a standing ovation and waves to the crowd. Olynyk then helped beat his old team, which really wasn't interested in bringing him back after last season.

"It was definitely satisfying, not only because of how the game went but we dropped one two nights ago (in Atlanta) that was pretty big for us," he said, "and to come in here and steal one on their court is not an easy thing to do."

Asked about the tribute, Olynyk, who nailed six of his eight 3-point attempts and was 12 of 15 overall from the floor, said, "It's special. Just all the love and support they've given me, from the organization, from the team, to the city, to the fans. It's special to come back here and play in front of them, it's something that's special.

"For them to recognize you and honor you like that, that's something that doesn't always happen. I'm really thankful for everything they've done to help me get to where I am and be the player and person I am."

And will the Celtics fans still love him?

"I hope so," he said. "They're going to be fine. ... They've got a lot of wins, but they're going to be fine."

Celtics coach Brad Stevens said, "He played a great game. I'm certainly happy for him. It was definitely at our expense. Second time in a week one of our former players came in and gave it to us (Utah's Jonas Jerebko was the other)."

The story almost had a lousy ending for Olynyk and his team, as Irving, who basically brought the Celtics back by himself, missed the last shot.

Irving helped Boston recover from a late 11-point deficit and finished with 33 points. He had an open look and let it fly for the win after a timeout with 6.2 seconds left, but he missed for the 13th time in 24 shots on the night.

"I'm not sure there's too many players you'd rather not be looking down the barrel at you with four or five seconds to go, ball in his hands, he can create a look, a clean look," Miami coach Erik Spoelstra said. "Sometimes you also need to be lucky."

The Heat (16-15) were playing without four players, including Hassan Whiteside and Justise Winslow, and they fell behind by 12 in the first half. They led by 11 with 2:46 left, and Irving was responsible for all but one of the final 13 Boston points, scoring nine and assisting on three with a behind-the-back pass.

The win ended a four-game TD Garden losing streak for Miami and gave the Heat a 2-1 season series victory against Boston this season.

The Celtics (26-8) are just 4-4 in their past eight games overall.

Olynyk also grabbed seven rebounds, while Miami's Josh Richardson scored 19 points and had six assists and Dion Waiters scored 10. Jordan Mickey, also a former Celtic, came off the bench to contribute eight points and eight rebounds in the win.

Irving finished 3 of 9 from 3-point range and added five assists. Boston's Jaylen Brown scored 16 points (12 in the first quarter, the other four late), Marcus Smart 15 and Jayson Tatum 11.

Smart hit four 3-pointers late in the third quarter and into the fourth. Tatum dislocated his right pinkie in the first half but returned with it taped. He said his finger was "just like throbbing" but that he would play in New York against the Knicks on Thursday night.

NOTES: Boston C Al Horford fouled out on three quick fouls in the fourth quarter, the last two four seconds apart. "There wasn't anything there," he said. "Yeah, that's tough." ... Miami coach Erik Spoelstra on his team's injuries, with 49 points, 25.4 rebounds and 8.7 assists per game missing Wednesday night: "This is a world we live in. Look around the league. It can be a lot worse. You have to deal with a lot of things in an 82-game season. Everybody goes through their moments at some point. We're going through ours right now. We're not making excuses for it." ... The Heat open a four-game homestand against the Dallas Mavericks on Friday night.