Jayson Tatum, left, and the Celtics finished off Atlanta in the first round and will face Joel Embiid, right, and the 76ers in the Eastern Conference semifinals. Chris Szagola/Associated Press

ATLANTA — Bring on Philly.

The Boston Celtics finally finished off the Atlanta Hawks, winning the opening-round series in six games with a 128-120 victory Thursday night.

Now, the second-seeded Celtics can turn their attention to the well-rested Philadelphia 76ers for a matchup between the two highest-seeded teams left on the Eastern Conference side.

Game 1 is Monday night in Boston.

“We know they’re gonna bring the fight,” Boston star Jaylen Brown said. “It’s gonna be fun. They’ve (got) some great players in Joel Embiid and James Harden. It’s gonna be a test again. We have to be ready to fight again. I’m up for it. I can’t wait.”

With top-seeded Milwaukee stunningly knocked out by Miami, the Celtics-76ers winner will surely be viewed as a big favorite to advance to the NBA Finals.

The Celtics have essentially been in championship-or-bust mode since losing to Golden State in last year’s finals.

That was evident in the closing minutes against the Hawks, who had pulled off an improbable comeback in the previous game at Boston to extend the series.

Atlanta seemed on the verge of forcing Game 7 until the Celtics clamped down defensively and ripped off an 11-0 run that broke open a game that was tight all the way.

“I thought our guys did a great job at the end of just locking in,” Celtics Coach Joe Mazzulla said. “They wanted to win. They kept the momentum, the energy, the edge of the game, and they executed.”

By making quick work of the Nets, third-seeded Philadelphia has been able to give Embiid some extra time to rest his ailing right knee. The 76ers haven’t played since last Saturday.

Embiid sprained the lateral collateral ligament in Game 3 against the Nets. He didn’t play in the series clincher, and the 76ers haven’t said if he’ll be ready to go against Boston.

Embiid’s availability will be a huge factor, obviously, especially considering how closely these teams were matched during the regular season.

Boston won three of four meetings, but the margin was single digits in every game. The Celtics (57-25) finished just three games ahead of Philadelphia (54-28) in the conference standings.

Brown, who averaged 26.7 points in the opening round, said the tougher-than-expected challenge from the Hawks should benefit the Celtics going forward.

“In the playoffs, you’ve got basketball, you’ve got execution, and you’ve got just the fight that’s kind of going on,” he said. “Atlanta might not have all the Xs and Os, but they fought us. They offensive rebounded with us. They played hard, they had effort, and they used their athleticism. They didn’t back down from no challenges. That’s what we needed to step up.”

For Mazzulla, it was good to get a playoff series victory under his belt.

Mazzulla has been lauded for the job he did under stressful circumstances, taking over the head job after Ime Udoka was suspended and then fired for an inappropriate relationship with a female Celtics employee.

Mazzulla blamed himself for the Celtics squandering a 13-point lead in the fourth quarter of Game 5, denying them a chance to wrap on the series on their home court.

But he made all the right calls in Game 6, especially at the defensive end as the Celtics mixed and matched their coverages to stifle Hawks star Trae Young down the stretch.

“He’s been great all season – just managing personalities, managing games.” All-Star Jayson Tatum said. “He always finds a way to maintain his poise. That’s important. When things are going great, stay the same. When things are not going great, stay the same.

“He’s done a great job.”