But the Magic made a key offseason pickup of their own.
Carter, who came to Orlando in the offseason as part of a five-player trade, took 29 shots, a season high and his most in almost three years.
"I'm just glad I was able to deliver," he said. "This type of basketball game, you don't want to let down. This is what it's all about. This is the bar. It's great to see we were able to buckle down and persevere."
Rashard Lewis had 16 points and 10 rebounds, Dwight Howard grabbed 15 boards and Mickael Pietrus added 14 points for Orlando, which won the rematch of last season's Eastern Conference semifinals for its fourth consecutive victory.
"This is a big game for us, a confidence booster," Lewis said. "We rode Vince a lot tonight."
Paul Pierce scored 21 points, Garnett scored 13 with 11 rebounds and Ray Allen had 15 points for the Celtics, who have lost three of their last four games and three of five at home. Wallace had 13 rebounds, but he was 0 for 8 from 3-point range and Boston was 2 of 19 from beyond the arc as a team to contribute to a 34.5 percent overall shooting percentage.
"I think that our team is playing awful," coach Doc Rivers said. "I've been saying it for a week now. We're going to win some games still, but we're not going to win against good teams."
The game was the first meeting between the teams since the playoffs, when Orlando rallied from a 3-2 deficit to advance and, after beating LeBron James and the Cleveland Cavaliers, reached the NBA Finals. It was the first time in franchise history that the Celtics lost a series after going into Game 6 with a chance to clinch.
The teams seemed destined to meet up again next postseason: They had matching 9-3 records entering Friday night's game that were tied for the second-best in the conference to Atlanta. Now the Magic, who already held bragging rights thanks to last year's playoff win, took the early lead in the race for this year's seeding.
"We're not a team that takes losing well," Garnett said. "We're still trying to figure it out."
Kendrick Perkins picked up his fifth foul -- and a technical to go with it -- with 7:25 left in third and played only 15 minutes in all. Wallace took most of his minutes, hitting from under the basket with 2:53 left to tie the game 78-all.
Carter made a 12-footer to break the tie with 2:33 to play and give the Magic the lead for good. Lewis made a pair of free throws with 59 seconds left, then Jason Williams stole the ball from Allen to clinch the victory.
The Magic scored 12 straight points after trailing 6-5, the Pietrus made a 3-pointer and a 19-footer at the end of the first quarter to make it a 16-point game. But Boston scored seven in a row to start the second, then went on a 12-3 run just before the half to make it a 41-40 deficit.
Orlando led by 10 in the third, and 66-59 heading into the fourth before Boston cut it to one point when Wallace had a steal, leading to Pierce's fast-break layup that made it 75-74 with 5:16 to play.
- The Celtics shot 33 percent in the first half.
- Carter passed Rick Barry and moved into 53rd on the career scoring list with a driving jumper with 9:34 left in the first half that made it 31-20.