If a larger role arrived, they would be ready.

“So, I feel like that was a blueprint right there,” Horford said. “This year, I just think that guys are comfortable playing in that situation. The biggest thing is everybody is bought into what Joe [Mazzulla] is telling them, and he’s just running a really good program over there … so that’s why it’s not surprising, their success.”

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Horford almost seemed to know what was coming. About an hour later, his undermanned new team took the court against his surging old one, and the Celtics pulverized the Warriors with a precise, punctual offense.

Midway through the third quarter, Boston had roared to a 34-point lead. The Warriors, to their credit, did not wilt. But their frenetic comeback eventually stalled because the initial hole was too deep, and the Celtics secured a 121-110 win in their first game since the All-Star break.

Golden State Warriors center Kristaps Porziņģis smiles while wrestling for the ball with Boston Celtics guard Payton Pritchard.Jeff Chiu/Associated Press

Boston has won seven of its last eight games and appears to be finding its stride as the playoffs begin to inch closer, with Tatum’s potential return making possibilities even more intriguing.

“At the end of the day, coming off the break, I thought our guys had a great attention to detail and a great purpose to what we did,” Mazzulla said.

Jaylen Brown had 23 points, 14 rebounds, and a career-high 13 assists to lead Boston. Payton Pritchard scored a game-high 26 points. The Celtics made 51.6 percent of their shots, hit 17 of 40 3-pointers, and dished out a season-high 36 assists.

“I think we hit the ground running and set our mind to coming off this break and not easing into it,” Pritchard said. “We wanted to come in full force.”

Horford and Kristaps Porzingis, who was acquired from the Hawks earlier this month, played their first game against the Celtics since departing last summer. Both came off the bench, with Porzingis registering 12 points and Horford adding 5 on 2 of 10 shooting.

“I felt all right,” said Porzingis, who has been limited to 18 games this year because of injuries. “Far from being in perfect shape. But I think for the first game back after a while, getting some energy back, I’m feeling good.”

Porzingis arrived in Golden State because he was just traded here, but Horford chose to sign with the Warriors last summer in large part because he believed the team had a clearer path to an NBA title than the Celtics and their reshuffled roster.

When asked about that choice prior to this game, he had a fairly cryptic response, saying it was “deeper than just the basketball stuff,” but declined to go into more detail. Nevertheless, this is certainly not what he imagined.

Star forward Jimmy Butler is out for the year after tearing his ACL, and star guard Stephen Curry remains out indefinitely with a knee injury. So Golden State is toiling in eighth place in the Western Conference, zapping some of the intrigue from what had become one of the NBA’s best rivalries over the past decade.

Thursday’s matchup at the Chase Center felt like the dawn of a new, less captivating era.

The Celtics led, 36-32, after one quarter and started the second by hitting three 3-pointers in a row. Then a reeling Warriors defense that could not keep up with their quick strikes and timely cuts, with Brown leading the way with seven first-half assists and Boston registering 21 as a team.

Mazzulla said the best way to combat Golden State’s offense is with a precise offense of their own, and he said the Celtics’ lack of live-ball turnovers helped keep them aligned as they marched to their big lead.

After a Porzingis 3-pointer pulled the Warriors within 63-48, the Celtics closed the half with a dizzying surge. Sam Hauser hit a 3-pointer before a beautiful ball movement-heavy possession ended with a Pritchard 3. Then Hauser hit another 3 with 34.3 seconds left, setting up Pritchard’s pull-up jumper that sent Boston to halftime with a 74-51 lead.

The third quarter unfolded similarly and that gap widened to 95-61. With 2:38 left, Pritchard reached in and forced a jump ball against Porzingis. Neither player wanted to let go of the ball after the whistle, with both holding tight as they walked toward midcourt.

Pritchard finally relented and both were smiling at the end.

“I’m disappointed in myself for letting that go,” he said later, smiling. “But, yeah, next time I’m not doing that.”

But the moment was a reminder that Porzingis and Horford are no longer Celtics, and that Boston has no intentions of letting up without them. The Warriors did just enough to ensure that the Celtics’ starters did not receive the rest of the night off, as they sliced the massive deficit to 117-106 on a Horford layup with 2:57 left. But the Celtics pushed back before it could become a significant worry.

“The last 10 ½ minutes Golden State took it to a different level,” Mazzulla said, “and we were forced to be poised, we were forced to make plays, and we were forced to make shots and get stops.”

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him @adamhimmelsbach.