The Celtics entered Sunday’s regular-season finale against the Magic locked into the No. 2 seed in the Eastern Conference playoffs, so they rested eight top rotation players before the most important games arrive.
Orlando, meanwhile, had a chance to push into the No. 6 seed and avoid the play-in tournament. Or, at the very least, a win could guarantee them a home game in it.
Jayson Tatum, Jaylen Brown, and Derrick White led a star-studded group of Celtics watching from the bench in street clothes. But within the locker room, there was little doubt that the collection of castoffs and rookies would be worthy replacements, even against a team still jostling for playoff seeding.
Celtics (from left) Nikola Vucevic, John Tonje, Jaylen Brown and Jayson Tatum were enjoying the action from the bench in Sunday’s regular season finale.Matthew J. Lee/Globe Staff
“Luka [Garza] said it before the game,” guard Ron Harper Jr. said. “This is for all the times that we’re on the bench, all the times that we wanted an opportunity. We had a chance to go out there and show it. I just feel like we all went out there with the utmost confidence.”
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The TD Garden crowd might have been less convinced at the start, especially as the Magic raced to an 11-point lead. But the Celtics pummeled Orlando with a massive third-quarter rally, then held off its late surge and emerged with a 113-108 win when Garza broke a tie by hitting a contested 3-pointer with 31 seconds left.
By the game’s end, the arena throbbed with playoff-level intensity and joy. A night many outsiders viewed as a throwaway game for the Celtics instead transformed into one of the most surprising results of this NBA season — just not necessarily for those who took part in it.
“I think going into the game we were expecting to go out there and compete and win the game,” Baylor Scheierman said.
The eighth-seeded Magic will visit the seventh-seeded 76ers in Wednesday’s play-in game; the winner will face the second-seeded Celtics in the opening round beginning at 1 p.m. Sunday. The play-in had originally been slotted for Tuesday, but the NHL Flyers are playing their regular-season finale then — so the Celtics will have to wait an extra day to learn their opponent.
If the Magic emerge, it is unlikely that their inability to put away Boston’s third string will give them great confidence. If the 76ers advance, they will be without star center Joel Embiid, who is out indefinitely after undergoing an emergency appendectomy Thursday.
But the Celtics weren’t really thinking about any of that Sunday. They were just basking in the unlikely victory that gave them 56 wins and closed this powerful regular season.
“I think it proves the type of locker room that we have,” coach Joe Mazzulla said, “the type of players that we have.”
Ron Harper Jr. (left) bursts away from a fallen Magic defender Tristan da Silva during his 27-point effort Sunday.Matthew J. Lee/Globe Staff
Scheierman had 30 points to lead Boston, and Garza and Ron Harper Jr. added 27 apiece. The Celtics made 22 of 22 free throws, and hit 12 of 25 second-half 3-pointers.
Paolo Banchero and Jalen Suggs had 23 points apiece for Orlando. The Magic committed 19 turnovers and made just 12 of 43 3-pointers. Some puzzling moves from coach Jamahl Mosley exacerbated the struggles.
Starting guard Desmond Bane played six minutes in the first quarter and was not seen again through the third, indicating his night was over for some reason. But then he returned early in the fourth after his team had spent the entire third capsizing. It ended up being too late.
The Celtics trailed by 9 at halftime but outscored the Magic, 42-20, in the third and held a 101-85 lead, their largest, with under nine minutes left. Then the Magic seemed to decide to start playing hard. They went on a 14-3 run over less than five minutes, and Bane’s 3-pointer with two minutes left made it, 108-104.
Wendell Carter made one of two free throws to make it a 3-point game. After John Tonje missed a 3-pointer, the Magic rushed upcourt and Jalen Suggs hit a 3-pointer with 36.4 seconds left to tie the score.
The Celtics called a timeout and were seeking a two-for-one chance. Garza’s contested 3-pointer from the left arc was not a clean or necessarily good look, but it went in anyway.
“I just knew I wanted to get it off quick, and obviously I tried to face up and it was kind of a wild shot,” Garza said, “but I’m glad it went in.”
Baylor Scheierman (55) makes a key block of a bid by Orlando’s Franz Wagner (left) late in the fourth quarter of Sunday night’s Celtics win.Matthew J. Lee/Globe Staff
Wagner and Suggs missed potentially game-tying 3-pointers at the other end, and Boston held on for the stunning victory.
Now, most of the players involved will step aside and yield the stage to Tatum, Brown, and the other stars as the postseason begins. But for one night, at least, they provided a reminder of the competitive culture that has been constructed here.
“I’m glad we all capitalized on that moment,” Harper Jr. said, “and it was just a great team win.”
Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him @adamhimmelsbach.