The Celtics found themselves in a hole against the Hawks. Doing what they do best helped them flip the script.

Grant Williams (center) hit two consecutive three pointers from in front of the Hawks bench to help seal the Celtics' victory on Tuesday.Jim Davis/Globe Staff

The Celtics’ elite defense has been the foundation of their resurgence. But there was some regression over the last two games, and then in the first half Tuesday night against the visiting Hawks, All-Star Trae Young mostly did as he pleased.

Suddenly, the Celtics were in danger of falling to a team with a losing record for the third time in five games. But in the locker room at halftime, after Boston surrendered 65 points and faced a 14-point deficit, there was no angst or panic.

The team reviewed some clips of where it had erred. It vowed to defend better without fouling.

“No yelling and screaming,” coach Ime Udoka said. ”It was more like, just get back to who we are defensively, what we’ve done.”

Then the third quarter began, and the Hawks were held without a point for more than four minutes. The Celtics went on a 14-0 run and relied on their defense after that. Atlanta mustered 33 second-half points, and the Celtics flipped their deficit into a 107-98 win.

With significant challenges looming against the Grizzlies (Thursday) and Nets (Sunday), Boston reclaimed its identity before a mild funk could swell into something more.

“We can’t let doubt creep into our minds,” guard Marcus Smart said. “We’re going to have games like this. It’s just how we respond. We just challenged ourselves to go out there and respond. We want to be the first team to hit in that second half, and we did.”

And they did it without star forward Jaylen Brown, who suffered a right ankle injury when he took a bad step on a drive less than three minutes into the game. Replays looked gruesome, with Brown’s ankle turning much more than an ankle is meant to turn, and Brown screaming in pain.

But the Celtics are confident that the forward avoided a significant injury. He walked off the court without assistance and without a noticeable limp. Udoka said he even tested the ankle in the bowels of the arena and wanted to return to the game, but the team erred on the side of caution.

Jaylen Brown howls in pain after twisting his right ankle in the third minute of Celtics' win Tuesday against visiting Atlanta. Brown walked off under his power, but did not return to the game.Jim Davis/Globe Staff

Afterward, Udoka said Brown was experiencing swelling and soreness, and that the team would monitor him in advance of Thursday’s game against the Grizzlies.

“With JB going down we knew the challenge was going to be hard for us,” Smart said. “Losing one of our best players, for us it means a lot [that when] somebody goes down, somebody else steps up.”

Jayson Tatum had 33 points, 8 rebounds and 7 assists to lead the Celtics, and Derrick White and Grant Williams added 18 points apiece. Boston held a 20-3 edge in second-chance points.

Young scored 31 points to lead the Hawks (29-32), but he was held to 9 in the second half, when Atlanta made just 13 of 39 shots and 2 of 16 3-pointers.

“Once you beat that one guy or beat that first line, we had somebody else ready to step up to the challenge,” Smart said. “So, that’s part of our defense. It takes all five of us and, when we’re all clicking on all cylinders, it’s really tough to score.”

Udoka said that the Celtics appeared “shell-shocked” following Brown’s injury. Williams covered his eyes on the bench. Smart winced and thought his teammate had suffered a knee injury. There was eventually relief, but it took some time.

The end of the first half was a bit of a mess, with the Hawks attempting eight free throws over the final 31 seconds thanks to some turnovers and awkward Celtics fouls, allowing Atlanta to take a 65-51 lead to the break.

But everything was a chore for the Hawks offense after that. The Celtics blitzed Atlanta with a 14-0 run, and then pushed in front later in the period behind White, who scored 9 consecutive Boston points to make it 82-75 at the start of the fourth.

Grant Williams had the TD Garden crowd roaring with a pair of second-half threes Tuesday night against Atlanta.Jim Davis/Globe Staff

After the Celtics’ lead swelled to 10 midway through the final quarter, Young converted a layup with 4:32 left, and the Hawks broke free on a fast break moments later. Smart was jogging back, exhausted and prepared to cede a layup, when he saw Tatum and Williams attempting to slow down the fast break on their own.

“Once I saw that it kind of gave me the little juice I needed to put my head down and go down and help,” Smart said.

Smart swooped in and blocked DeAndre Hunter’s layup attempt, and Williams connected on the first of consecutive 3-pointers at the other end to seal the win.

“All you see is Smart coming out of nowhere and he makes the play,” Williams said. “But it’s not like he just made the play and took off. He made the play and calmed us down.”