BOSTON — The Celtics put themselves out to a massive early lead, but the Cavaliers came all the way back to stun the reigning champs. By the final buzzer, the Celtics fell to the Cavaliers 123-116 on Friday at TD Garden in a thrilling finish. The C’s fell to 42-18 while the Cavaliers won their ninth straight game to get to 49-10.

The shorthanded Celtics blitzed the Cavs right from tipoff, sprinting ahead to a 25-3 lead as they made 7-of-9 of their 3-pointers. The Garden was rocking while the visitors got smacked in the mouth. But the Cavs quickly recovered from there, though they never grabbed the lead in the first half. Still, the No. 1 seed in the East showed gusto to rally back from their early deficit to make it a game.

While the Celtics went up big to start the third quarter again, the Cavs kept the pressure on. Finally, early in the fourth quarter, they took their first lead of the game after battling back from the early 22-point deficit. While the C’s battled themselves, the Cavs kept coming up with clutch buckets. That was all Cleveland needed as the Garden crowd — jovial to start the game — left with a disappointing result.

The C’s were without Kristaps Porzingis (illness) and Jrue Holiday (finger) as they had a tight rotation Friday. Jayson Tatum impressed all night with 46 points, 16 rebounds and nine assists. Jaylen Brown added another 37 points while Derrick White had 16 points. Donovan Mitchell was great as he finished with 41 points to lead the Cavaliers. Darius Garland poured in 20 points and seven assists.

The Celtics have another marquee game, hosting the Nuggets at 1 p.m. Sunday at TD Garden for their next game. Here are four takeaways from Boston’s loss to Cleveland:

Couldn’t finish: The Cavaliers never looked back after taking the lead late in the fourth quarter as the C’s couldn’t come up with enough shots and stops. While the Cavs missed shots in the fourth, they also collected seven offensive rebounds in the quarter to keep possessions alive. By the end, the Cavs refused to relinquish their own lead down the stretch. Mitchell was excellent down the stretch with key buckets as part of putting up 26 points in the second half.

Pouring it in: Tatum’s had some awesome games recently and Friday was the All-Star playing as one of the best players in the world. Tatum was aggressive right from tipoff, and while still setting up teammates, he also understood he was having one of those nights. The Celtics needed that production as they were shorthanded Friday, but it still wasn’t enough as the Cavs had a few extra makes. Tatum finished shooting 19-for-37 from the field as he put up a season-high in points Friday. But on the flip side, Mitchell was also awesome as the Cavs got contributions from their whole roster.

Bench production: The Celtics were down two starters Friday in Porzingis and Holiday as they had to dig deeper into their bench. As a result, the C’s featured a tight seven-man rotation with Payton Pritchard and Luke Kornet coming off the bench. Drew Peterson (one minute) and Torrey Craig (three) got some tick, but it wasn’t much. That was in contrast to the Cavs getting contributions across their roster as they finished with 33-6 edge in bench points.

Final matchup: The Cavs came into Friday’s game with plenty of juice — this was their last shot at the reigning champs during the regular season, after all. While it looked dicey early for the visitors, they scratched and clawed their way to the win Friday. They avenged their loss on their home court from earlier this month, splitting the season series with the reigning champs 2-2. While regular-season results don’t translate to the playoffs, the Cavs certainly sent a message Friday in what could be a potential playoff preview.

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