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.

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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.

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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.