BOSTON — The Celtics continued their climb up the Eastern Conference standings Monday night, routing the Chicago Bulls to claim sole possession of second place.

The 115-101 win at TD Garden pushed Boston ahead of the New York Knicks, who were blown out by the first-place Detroit Pistons earlier in the evening for their fourth consecutive loss.

The Celtics, now 23-12, have won four straight and eight of their last nine. They own the East’s best point differential this season and rank top-three in the NBA in offensive rating and net rating, far outpacing their lukewarm preseason expectations.

Jaylen Brown has been the primary driver of Boston’s success without injured superstar Jayson Tatum, but he struggled against Chicago, finishing with 14 points on 6-of-24 two days after dropping 50 against the Los Angeles Clippers.

Anfernee Simons and Payton Pritchard spearheaded the Celtics’ offense with 27 and 21 points, respectively. All of Simons’ scoring came in the second half. The backcourt duo combined to shoot 12-for-21 from 3-point range on an otherwise ugly shooting night for both teams.

Though the Celtics shot just 40% from the field — their fourth-worst mark of the season — they attempted 18 more shots than the Bulls. They dominated the offensive rebounding battle, particularly in the first half, grabbing 20 in the game to Chicago’s six.

Head coach Joe Mazzulla admitted his team looked “relatively tired” in its first game back from a five-game road trip, which included West Coast stops in Portland, Utah, Sacramento and LA. But the Celtics played with the effort necessary to avoid a trap-game letdown.

“I was not pleased with how they looked, but I was pleased with how they tried, how they played and how they competed,” Mazzulla said. “… For us to not shoot the ball well at all in that first half but to play well defensively, that’s a sign of a mature team. So it was impressive. I just liked their competitive spirit throughout the entire game.”

Boston will be back in action Wednesday night against the shorthanded Denver Nuggets, who will be without their three-time NBA MVP Nikola Jokic (knee).

After a sluggish start, Derrick White sparked the Celtics by helping force turnovers on consecutive Chicago possessions. Those led to a 3-pointer by Sam Hauser, who made his second straight start over Jordan Walsh, and a foul that sent White to the line for three shots. The Bulls committed six turnovers in the first quarter, including a pair of 24-second violations, and the Celtics turned them into 13 points.

Boston held Chicago to 14 total points in the first and closed the quarter on a 25-5 run. They dominated the second quarter, as well, and took a 54-33 lead into halftime.

As that scoreline suggests, it was not an impressive offensive half for either side. The Celtics shot 35.7% from the field and 28.6% from three. The Bulls were even worse, shooting 31.7% overall and 5-for-28 from deep (17.9%).

The difference? Boston controlled the margins, holding decisive edges in points off turnovers, offensive rebounding and second-chance points. That dirty work allowed the Celtics to build a 19-point halftime lead despite Brown having nearly as many giveaways (two) as made field goals (3-for-14) over the preceding two quarters.

“Our defense kept us in it,” Mazzulla said. “Our offensive rebounding kept us in. And as long as we can continue those margins, those are the things that allow you to play the way that you need to play when you’re not at your best from a shooting standpoint.”

Pritchard was the only player to score in double figures during the rock-fight first half, but he got there in exhilarating fashion, hitting an off-balance 3-pointer as time expired in the second quarter.

It was the first buzzer-beating three of the season for the Celtics guard, who made those shots his calling card during Boston’s 2024 championship run.

“Back to hitting buzzer-beaters,” Pritchard said after the game. “That might have been my first buzzer-beater that was a legit shot — not, like, at the rim — this year. So it felt good to hit one.”

Pritchard added two more conventional 3-pointers early in the third quarter. Then Simons, who had no points on 0-for-3 shooting before halftime, took over. He went 9-for-13 in the second half as the Celtics stretched their lead to 23.

During one second-half stretch, Simons scored 18 consecutive Celtics points. He then assisted on a pair of makes from Brown, who finally found some offensive momentum midway through the fourth quarter. Brown’s first 3-pointer of the night made it 104-86 Celtics with 5:37 to play.

“I think we kind of understood coming into the game how tough a game it was going to be, mentally and physically,” said Simons, who’s shooting 53.8% from distance on nearly 10 attempts per game during Boston’s four-game win streak. “Just coming off a long road trip, coming from the West Coast, practically being on the plane all day. And we knew that it was a possibility that we might struggle a little bit offensively, but I think defensively, through most of the first half, I think we played great. We were getting stops and making it a game. And I think that’s what helped us, for sure, just the defensive end, until the offense came along.”

But the Bulls, who shot the ball much more efficiently after halftime, staged a late rally. A Matas Buzelis triple cut it to 104-93 with 4:17 remaining, triggering a Mazzulla timeout. The Celtics responded with a Neemias Queta dunk and a long-awaited White 3-pointer — which snapped an 0-for-7 start from deep for the veteran guard — to wrest back momentum.

One last Simons three in the final minute iced the game. His 27 points in the second half — more than he’d scored in any of his first 34 full games in a Celtics uniform — were the most by a Boston reserve in the play-by-play era (since 1996-97).

Playing as Boston’s sixth man after three-plus seasons as a starter in Portland, Simons has been a consistent difference-maker of late. The 26-year-old entered Monday with the third-best plus/minus in the NBA since the start of December.

“(He’s) just a guy that has come in with a great attitude,” Mazzulla said. “He’s happy to be here, wants to do whatever it takes to win and has an understanding in that, but also super confident. You’ve seen there are some games in that run that he’s been on (where) his stint has separated the game for us. But where he’s really been the most consistent is the defensive end. The physicality on the defensive end, executing our schemes, executing our coverages, playing with the level of physicality, that’s where he’s been at his best. He just comes up every day, wants to work, wants to play hard, wants to win, so he’ll do what it takes.”

The Celtics, whom many pundits viewed as a play-in team or worse after their offseason overhaul, now trail only the Pistons in the East standings with the season nearly halfway complete. But Pritchard, one of four healthy rotation players still left from the 2024 championship squad, isn’t celebrating yet.

“I take a lot of pride in being first in the East, and we still need some work to get to that point,” he said. “So that’s the main goal.”