Jaylen Brown drives to the basket against Atlanta’s John Collins during the first half of Boston’s 112-99 win in Game 1 of the Eastern Conference quarterfinals Saturday at TD Garden. Michael Dwyer/Associated Press

BOSTON — After an opener that went from rout to flirting with catastrophe, the Boston Celtics got both a win and an early reminder of how lulls could spell doom in the playoffs.

Jaylen Brown had 29 points and 12 rebounds, and the Celtics capitalized on a woeful shooting performance by the Atlanta Hawks to hold on for 112-99 victory in Game 1 of the Eastern Conference first-round matchup on Saturday.

Jayson Tatum scored 25 points, 21 in the first half. Derrick White finished with 25 points and 11 rebounds for Boston, which hosts Game 2 on Tuesday.

“We expect to get their best shot,” Brown said. “We let them get a little more comfortable in the second half, so I expect the next game for them to be a little more prepared. So we’ve got to be a little more prepared as well.”

It was Brown’s first game since missing the final two of the regular season with a cut on a finger on his shooting hand. He played with tape and wrap.

He played through pain, hitting on 12 of 23 field goal attempts, but had six turnovers. He said it as hard to grip the ball and his hand “split open” at one point. It will be examined Sunday.

The No. 2-seeded Celtics led by as many as 32 points, pouncing on an Atlanta team that missed its first 10 3-point attempts and shot 5 of 29 from beyond the arc for the game.

Atlanta used a 32-12 run to cut the deficit to 96-84 on a three-point play by Bogdan Bogdanovic early in the fourth.

The Celtics got the lead back up to 107-87. It was 110-97 with less than two minutes to play when Atlanta’s De’Andre Hunter got free on fast break. But his layup attempt was blocked by Marcus Smart.

“Human nature plays a part. But we don’t want things like that to haunt us,” Tatum said.

Smart, last season’s NBA Defensive Player of Year, finished with three steals and two blocks.

Dejounte Murray led the Hawks with 24 points, eight rebounds and six assists. Trae Young added 16 points.

“You can’t be down that much and expect to come back and win,” Young said. “But we still fought. We were being aggressive in that second half.”

Despite Atlanta’s late push, the Celtics sizzled from all points on the floor, connecting on 13 3 pointers.

After dropping in his third 3-pointer in the closing seconds of the first half, Tatum spread his arms out wide as he backed down the court to an ovation from the TD Garden crowd.

A big part of Boston’s game plan coming in was neutralizing Young and Murray, Atlanta’s top two scorers. The Celtics did that and a lot more in the first three quarters.

Young missed his first six shots beyond the arc and was 5 of 18 from the field. Murray was 10 of 25 from the floor.

In a move to match Atlanta’s speed, Boston went small, starting White instead of big man Robert Williams in a lineup alongside Al Horford, Tatum, Brown and Smart.

It seemed to neutralize the Hawks’ attack.

Young had an especially rough start. He had a pass the first possession of the game stolen by Brown and had his first field goal attempt blocked by White on the way to missing his first six shots.

Atlanta Coach Quin Snyder said before the game a point of emphasis would be not to turn down open 3s or be deterred by misses.

That wish was tested as Hawks shot 9 of 25 from the field in the opening period and 0 for 9 from beyond the arc as the Celtics took to a 29-19 lead.

Despite the late drop-off, Celtics Coach Joe Mazzulla said he’s not worried about the late-game malaise carrying over.

“I’m not concerned at all,” he said. “This team has played great for the entire season. That’s going to happen. It’s actually good that we went through it. We had to feel that and it’s important that we learn from it.”

TIP-INS

Hawks: Outscored the Celtics 31-20 in the third quarter. … Young’s 28-footer early in the second quarter was Atlanta’s first made 3 of the game. Atlanta shot 1 of 16 from 3 in the first half.

Celtics: It was Brown’s first game since missing the final two of the regular season because of a cut on a finger on his shooting hand. He played with tape and wrap, but it didn’t seem to affect him. … Boston outscored the Hawks 45-25 in the second quarter. …Tatum had 13 first-quarter points. … The seats inside TD Garden were draped with T-shirts that read “Unfinished Business,” a reference to Boston’s run last season that came up short in its NBA Finals’ loss to Golden State. The “I” and “S” in unfinished were both highlighted, with the “S” fashioned to look like an “8,” a nod to the 18th championship being sought by the franchise. … A host of Boston sports stars sat courtside, including New England Patriots owner Robert Kraft, Bruins players David Pastrnak, Charlie McAvoy, Hampus Lindholm and Jake DeBrusk, and former Red Sox star Dustin Pedroia.