BOSTON — Kyrie Irving had an answer for everything, and his back-to-back threes in overtime were too much for the 76ers to fight against.

The Sixers fell to the Celtics, 121-114, in overtime on Christmas Day at TD Garden despite 34 points from Joel Embiid and 24 from Jimmy Butler, in a thrilling game to the very end.

The Sixers were leading by five in OT after JJ Redick hit a technical free throw after Marcus Smart shoved Ben Simmons. But the Celtics were not deterred and went on a 13-1 run to close out the game.

“We lost,” Butler said. “Back to the drawing board.”

With under a minute to play in the fourth quarter, Wilson Chandler was alone in the paint with Irving, and the Sixers trailing by one point. Chandler, who finished with a season-high 15 points, stuck with Irving, forced him into a tough shot, and at the other end Chandler hit a three as the Sixers took a two-point lead with 36 seconds left in regulation.

Irving came back and hit a deep two over the top of Butler to tie things up and send the game into overtime. In the extra period, Irving scored six of his game-high 40 points to seal the victory.

“It’s always frustrating when that happens, but that shot he hit over Jimmy was tough,” Chandler said. “Jimmy was playing good defense though, played good D the whole game. That’s just Kyrie, though. He’s done it in the Finals, he’s done it his whole career.”

The Sixers spent a lot of their time this summer thinking about their second-round playoff loss to the Celtics, and they didn’t feel any better when they came to Boston on opening night and were reminded that they had a long way to go before they could battle with the NBA’s elite.

Tuesday’s game was marked on the calendar as a chance for Brett Brown to reevaluate how the team measures up. He left the game feeling like there were a lot positives to point to, but said closing out strong and maintaining composure at the end of the game is something that the Sixers will continue to work on.

“It’s a disappointing loss because of the last two minutes, two-and-a-half minutes of overtime. We were up and we turned the ball over," Brown said. “But I leave feeling like we’re not that far off.”

By the time the game was over, a lot of things we already knew about the Sixers were on display once again. The Sixers have an inconsistent bench whose players didn’t manage to get on the scoreboard until Landry Shamet hit a three-pointer midway through the third quarter.

“At the end of the day, you’re going to need more contribution from our bench,” Brown said. “Tonight, we weren’t able to get that.”

The Sixers still have trouble defending against crafty guards and struggle when switches exploit their weak points and Irving made them pay on Tuesday.

On the other hand, the Sixers also showed off their strongest attributes and proved that they are a little closer to being able to compete than they were before.

Embiid had another impressive first half, posting 19 of his 34 points and showing off his range and skill, hitting from everywhere on the court. But Embiid only scored two points in the fourth quarter and at the end of the night was left wondering why the ball moved away from him so much at the end of the game.

The Sixers flexed their defensive muscles in the third quarter, while Butler, who was not with the team on opening night, scored 13 of his 24 points.

Simmons gave a glimpse of what could be, showing that he has the ability to hit a long jumper, sinking a 22-foot turn-around shot in the fourth quarter when the shot clock was running out. But Simmons doesn’t look for those shots regularly and Brown noted that it’s a part of Simmons' game that needs to evolve.

Trailing most of the first half, the Sixers took the lead late in the third quarter, going on a run when Irving was resting. But the Celtics clawed back and the score toggled back and forth between the teams, in a game that featured nine lead changes and nine ties.

“I wished he would stay on the bench,” Brown said with a laugh. “I thought it would be a great Christmas gift from Kyrie to me ... Inevitably, you have to beat him. You have to beat them with him on the floor when it matters most.”

In the end, the Sixers weren’t able to fight through the last couple of minutes while Irving continued to put on a Christmas Day show.

The Sixers fell to 22-13 on the season, 6-10 on the road and will have four more games on the road against the Jazz, Trail Blazers, Clippers, and Suns before returning for their first home game of 2019 on Jan. 5 against the Dallas Mavericks.