ATLANTA >> Al Horford hit a huge 3-pointer against his former team and the Boston Celtics broke open a tight game in the closing minutes to finish off the Atlanta Hawks 128-120 on Thursday night for a 4-2 victory in the opening-round playoff series.

The second-seeded Celtics advance to face the third-seeded Philadelphia 76ers, who’ve been resting since completing their four-game sweep of Brooklyn last Saturday.

Game 1 is Monday night in Boston.

Boston ripped off an 11-0 run that included three straight 3-pointers, with Horford’s big shot sandwiched around 3s from Jayson Tatum and Jaylen Brown.

Tatum capped the spurt with a dunk, which gave the Celtics a 121-113 lead with 2:07 remaining.

Brown led the Celtics with 32 points, while Tatum had 30. Horford, who played in Atlanta from 2007-16, chipped in with 10 points and 12 rebounds.

After carrying the Hawks to an improbable victory in Game 5 at Boston, Atlanta’s Trae Young ran out of steam in the second half. He missed 12 of 13 shots over the final two quarters.

Young had 30 points and 10 assists, but he finished just 9 of 28 from the field.

Marcus Smart also came up big for Boston, scoring 22 points and brilliantly running the Boston offense down the stretch.

Dejounte Murray returned to the Hawks lineup after serving a one-game suspension for bumping an official at the end of Atlanta’s Game 4 loss.

Murray seemed a bit out of sync, missing all five of his shots in the first half. He was better in the second half but still managed just 14 points.

The Hawks needed a few more to keep their season going.

Young forced the series back to Atlanta with a long 3-pointer that stunned the Celtics 119=117 in Boston, capping the Hawks’ improbable comeback from a 13-point deficit in the fourth quarter.

Coming off his 38-point, 13-assist effort, Young kept it going with 18 points in the first quarter.

But the Celtics finally clamped down on the Hawks star, whose heroics had forced Janet Jackson to postpone her scheduled Thursday concert until Friday to make room for Game 6.

Now, State Farm Arena is wide open for the summer.

Embiid’s status uncertain for 76ers

CAMDEN, N.J. >> The Philadelphia 76ers still aren’t saying if Joel Embiid will be able to return from a sprained right knee and play next week in Game 1 of the Eastern Conference semifinals.

The 76ers completed a sweep of the Brooklyn Nets on Saturday, providing a great opportunity for Embiid to rest up. Embiid, an NBA MVP finalist, missed Game 4 with the knee injury. He has yet to practice ahead of Monday’s Game 1 against the winner of the Atlanta-Boston series.

Coach Doc Rivers said Thursday that Embiid was at a doctor’s exam while the team practiced at its New Jersey facility.

“I’m just going to wait,” Rivers said. “They’ll call me later and we’ll see where he’s at.”

The 29-year-old Embiid, from Yaoundé, Cameroon, averaged 33.1 points this season to win his second straight scoring title. He also averaged 10.2 rebounds and tied a career high with 4.2 assists per game. He played in 66 games, the second-highest total of his career.

Embiid missed two games in the second round last year and another in the first round in 2021 with various injuries, on top of the two he missed to begin the 2018 playoffs with an orbital fracture and another in 2019, also with a knee problem.

Whatever happens in the Hawks-Celtics matchup, Rivers said the extended series has increased the chances of Embiid playing in Game 1 in the next round.

“If we played on Saturday, I don’t know how realistic it would have been, so that’s a good thing,” Rivers said.

Embiid averaged 36.8 points and 11.8 rebounds in four games this season against the Celtics.

Leonard suffers meniscus tear

LOS ANGELES >> Los Angeles Clippers star Kawhi Leonard has a meniscus tear in his right knee, although his surgically repaired right ACL is intact.

The team had said Leonard sustained a right knee sprain after playing in the first two games of the Clippers’ first-round loss to Phoenix but didn’t provide further details.

The two-time NBA Finals MVP had an MRI in Los Angeles after Game 2, which showed the tear, according to Lawrence Frank, president of basketball operations.

“Regardless of the treatment, Kawhi will be ready for next year,” Frank said Thursday.

The team has yet to decide on a course of treatment, he said.