He finished with 29 points, plus 10 rebounds and 9 assists, but it required 29 shot attempts. Luka Garza added 20 points and nine rebounds in 28 minutes and Payton Pritchard scored 16 points, but the Celtics shot just 41 percent and committed 15 turnovers.
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Brown, who was sidelined with left Achilles tendinitis, took responsibility for the loss.
“That was probably one of my worst games of the season,” he said. “I missed a lot of easy shots. It was a very physical game, playoff-like atmosphere, and I didn’t think we adjusted quick enough. They came to play, the refs let a lot of stuff go and we didn’t adjust to the physicality.”
The Celtics, without Brown, defeated the Hawks at TD Garden, 109-102, on March 27 behind 36 points off the bench from Pritchard and 26 from Tatum. But Boston couldn’t maintain any offensive cohesion Monday after taking an early 6-point lead, then lost contact in the third quarter, when it was outscored, 36-22, while missing 15 of 20 shots.
“It was the third quarter,” coach Joe Mazzulla said. “It was tied at halftime. I thought we played pretty well. There was some empty possessions on the offensive end [in the third]. They hit some shots. We gave up too many layups. That got the best of us.”
Atlanta center Onyeka Okongwu, who missed all four of his 3-point attempts in the first half, made three in a 3:15 span of the third quarter as the Hawks went on a 21-8 run to take control. All five Hawks’ starters scored in double figures, including 20 points from Okongwu and Jalen Johnson.
Celtics center Luka Garza blocks a shot by Hawks forward Jalen Johnson in the first half. Mike Stewart/Associated Press
Boston finished 3-1 in a daunting four-game stretch that included two games with streaking Atlanta and matchups with Oklahoma City and Charlotte. But they couldn’t get that fourth win as the combination of Brown and Derrick White shot 12 for 41.
“I think just sometimes, we had good looks and their defense is pretty physical and they have good defenders that make it difficult,” White said. “When you play a team a couple of days ago and you play them again, it’s going to be, like, a little bit more difficult, and we weren’t able to execute.”
The lone effective Celtic was Garza, who scored 20 points with nine rebounds and a plus-6 in his 28 minutes. He couldn’t get the necessary support from his teammates who combined for 35.5 percent shooting.
Brown returned to the lineup after a two-game absence with Achilles tendinitis and looked rusty in the first half. He was sloppy with the ball, committing four turnovers in 18 minutes, two from just losing his dribble.
“I felt like I missed a lot of easy shots, especially at the rim,” Brown said. “I just didn’t make my free throws. This game is on me. I’ve got to be better. Probably one of my worst performances in a while and that cost us the game.”
With a chance to build a late first-half lead, Brown simply fumbled his dribble into the hands of defensive ace Dyson Daniels, who scored an uncontested layup to slice the Celtics’ lead to 52-51. White countered with a layup, but Nickeil Alexander-Walker evened the score at halftime with a triple.
Boston committed 10 turnovers in the first half, two of those by rookie Hugo González, who was pulled by Mazzulla after multiple miscues. Mazzulla also snatched Baylor Scheierman in the second quarter after he attempted a corner 3-pointer leaning out of bounds that caromed off the side of the backboard.
Mazzulla went deep into his bench for center help, using rookie Amari Williams, who had his moments with a tip-in and six rebounds, and Charles Bassey, on the final days of his second 10-day contract. Bassey contributed rim protection with consecutive blocks on layup attempts by Jonathan Kuminga and Alexander-Walker. He also added a putback.
The Celtics actually outrebounded the Hawks and won the second-chance point battle, 17-8, but were just 15 for 37 in the paint.
Gary Washburn is a Globe columnist. He can be reached at [email protected]. Follow him @GwashburnGlobe.
