Jaylen Brown etched his name alongside Larry Bird’s in the Celtics record books Sunday night in Portland. But his milestone came in a losing effort.

Brown scored 37 points to tie Bird’s franchise record of nine consecutive 30-point games, but it wasn’t enough in a 114-108 loss to the Trail Blazers that snapped Boston’s four-game win streak.

The Celtics received limited offensive production from Brown’s supporting cast — Derrick White, Payton Pritchard and Sam Hauser combined for just 21 points and went 6-for-26 from 3-point range after scoring 73 in Friday’s victory over Indiana — and committed 20 turnovers, including four in the final 68 seconds.

“For most of the game, I thought our offense from a process standpoint was pretty good,” Celtics head coach Joe Mazzulla told reporters. “Obviously, not at the end in our late-game execution. But you have to give credit to Portland. They played well.”

Mazzulla’s troops also struggled to contain 7-foot-2 center Donovan Clingan (18 points, 18 rebounds, seven offensive boards) and wing Deni Avdija (24 points, 10 assists, seven rebounds). They, along with guard Shaedon Sharpe (26 points), powered a Portland team that was missing more than a half-dozen injured players, including ex-Celtics Jrue Holiday (calf) and Robert Williams III (knee management).

Holiday has not suited up since Nov. 14. Williams has yet to face his former team since the Celtics traded him away in 2023.

Anfernee Simons, who played seven seasons with the Blazers before being traded for Holiday this summer, went 4-for-11 and was a team-worst minus-15 in his first game back in Portland. He finished with 13 points.

The 19-12 Celtics will continue their season-long five-game road trip Tuesday in Utah (9 p.m. ET). The Jazz sit well below .500 at 12-19, but they’ve already beaten the C’s once this season and are coming off consecutive wins over the Detroit Pistons and San Antonio Spurs.

Brown got off to a strong start Sunday with six points in the opening two minutes and 13 in the first quarter. The Celtics also were able to harass Portland into a slew of early turnovers (seven in the first; 21 for the game). Simons forced two of those after receiving a tribute video and an ovation from the Moda Center crowd, then drilling a 3-pointer on his first touch off the bench.

Boston had a difficult time matching up with Clingan, however. The former UConn star reached double-double territory midway through the second quarter by feasting on offensive rebounds and putbacks. His production in the paint, coupled with the Celtics’ own sloppy ball security, helped Portland build a 41-34 lead.

Foul trouble also forced Mazzulla into some early substitutions. He lifted Jordan Walsh for Hugo Gonzalez after the former was whistled for three fouls in the first 4:30 of game time.

As effective as Walsh has been since his mid-November promotion to the starting lineup, high foul counts have been an issue for the 21-year-old wing of late. Walsh also committed two in the first five minutes of a loss to the Detroit Pistons on Dec. 15 and two in the first three minutes Friday against the Pacers.

Gonzalez, who boasts the best plus/minus of any NBA rookie this season, wound up playing 14 first-half minutes and stuffing the stat sheet with eight points, three rebounds, two assists and two steals. His takeaways came in quick succession, and he punctuated the second with a fast-break dunk. On the next Celtics possession, Gonzalez drew a foul on an offensive rebound and made both free throws to tie the game at 41-41.

Brown reasserted himself as the first half wound down. He poured in 10 points in the final 2:09 before halftime, including a buzzer-beating stepback 3-pointer that put Boston ahead 63-55. Brown had 27 in the first half on 11-of-16 shooting, then matched Bird’s 30-point streak with a free throw at the 5:28 mark of the third. In so doing, he also leapfrogged Bill Sharman to move into 12th place on the Celtics’ all-time scoring list.

The Celtics’ new No. 1 option has thrived this season while longtime co-star Jayson Tatum recovers from Achilles surgery. Brown, who entered Sunday averaging a career-best 29.4 points per game, has scored at least 30 in every game he’s played in December, plus three of his final four in November. In the lone outlier, he turned in a 19-point, 12-rebound, 11-assist triple-double.

Mazzulla said a scoring streak like Brown’s is “extremely difficult” to achieve.

“And not even that, it’s even harder for a guy like him to play balanced basketball and play team basketball,” the coach told reporters. “… Not only is it extremely difficult to do that, it’s extremely difficult to play well-balanced basketball, and I think it’s something that he does consistently for us, whether it’s his playmaking or his defense.”

But the Blazers outscored Boston 31-22 in the third quarter, including an 11-3 run that featured back-to-back threes by Toumani Camara and a vicious putback dunk by Clingan over Luka Garza.

Garza, the Celtics’ second-string center, halted that run with a 3-pointer, but he picked up his fifth foul shortly thereafter, prompting Mazzulla to send in his first small-ball lineup of the game. With two guards and three wings on the floor, Simons proceeded to score eight straight points to quickly erase another seven-point deficit. Boston entered the fourth quarter down 86-85.

Trailing by three with 7:05 to play, the Celtics won a challenge to wipe out a Hauser shooting foul, then got rapid-fire threes from Hauser and Gonzalez to tie the game at 98-98. Gonzalez was the only Boston bench player to post a positive plus/minus in the loss, finishing with 13-6-5 and a plus-3 in 30 minutes.

Three minutes later, Brown was assessed a flagrant offensive foul on a hard drive to the basket, but Advija missed both free throws, and Portland came up empty on the ensuing bonus possession. A Neemias Queta dunk at the other end cut it to one with 3:22 to go. Sharpe and Brown then traded threes.

But Brown, with a chance to put Boston ahead, had his pocket picked by Sharpe with 1:08 remaining, leading to two Blazers free throws. White responded with a three, but two late miscommunications between him and Brown, coupled with one final second-chance bucket by Clingan, secured the win for Portland.

White accepted blame for the costly late-game lapses.

“It’s all my fault, and I’ve got to be better,” the veteran guard told reporters. “Especially in a moment like that.”