ATLANTA — At halftime last night, the Celtics were falling apart on the court and, apparently, in their dressing room, as well.

Down 53-38 to the Hawks after playing a putrid 24 minutes, they were taking it out on each other before Paul Pierce stopped the noise.

“Doc (Rivers) came in and just wanted to tell guys what was wrong,” said Pierce, “and it just seemed like we were looking at one another and it was just like, you know, we’ve got to be able to accept coaching. Doc’s telling them what’s wrong, and, you know, guys are getting mad at him. And I’m like, this ain’t it. Don’t get mad at Doc. He’s coaching. We’ve got to get mad at this other team. It was needed.

“We had to bring the fight to them,” the captain said. “I think we were kind of bickering at each other a little bit too much, figuring out what kind of defense we run. That was a little bit too much for me. I just had to say, you know, ‘We’re fighting against one another. It’s against the team out there on the court. And once we realize that, we can play some ball.’

“And we stepped up that third quarter and played the type of ball that we know we can play.”

The result was a 51-28 second half and an 89-81 win on the second night of a home/road back-to-back.

Pierce then put the need for Celtics action into perspective, bringing in the longer-term picture, as well.

“I think there’s more of a sense of urgency because we know now there’s no more excuses,” he said. “I mean, we know what we can do defensively when we set our mind to it and we put the effort out there. But it’s got to be night in and night out. I’m tired of seeing flashes of it for six minutes and then take six minutes off.

“I’m tired of that now. I don’t have too much left in the tank as far as my career, so this is it. I feel like the East is wide open. It’s anybody’s game. I think we’ve got a tremendous opportunity.”

Terry takes attendance

Jason Terry returned to his first NBA home last night, and while he has fond memories of the city and people he met here, his affection and sentimentality were pretty much left at the door.

The Hawks were 149-261 in his five years here, and the crowds in the then-new Philips Arena reflected the on-court struggles.

“The losing was the toughest part,” said Terry. “Year after year, you’re not going to the playoffs. People just wouldn’t come out. I had some fans, but my 30 or 40 fans, that’s not going to fill Philips Arena. That was tough.”

Terry has seen the difficulty pro teams have had drawing in this town. The Braves were an easy ticket even in their best times, and the city has lost two NHL teams.

He believes it’s a demographic issue.

“There aren’t a lot of native Atlanta people, and that’s the biggest problem,” Terry said. “There are a lot of people from other places living in Atlanta, and they don’t have that same feeling for the home team like the people in Boston do.

“When you’re living where you grew up, the home team is your team. It’s tough to get that in Atlanta. It may take a while for the generations to come through.”

And, Terry added, it may take even more than that for the Hawks to thrive.

“I think they have to win to draw people, but, again, they have won and they still had trouble getting people to come to the games,” he said. “They’ve had good teams here over the years.

“I think they’ve got to win a championship probably more than anything, because they have won and had good teams. They’ve been in the playoffs the last four or five years, but they just haven’t hit that next step as far as support. Sometimes that’s what it takes. Maybe you have to win it all to get people in.”

Wilcox in limbo

Chris Wilcox is on the trip, but he still has no definitive timetable for a return from his sprained thumb.

Wilcox said he is scheduled to be examined Tuesday and hopes at that time to know when he’ll be able to come back to the lineup. . . .

Jason Collins is battling a hamstring problem. The Celts wanted to sit him, but he went 3:52 against the Hawks, making his only shot.

“He came in and did his job on one leg basically,” said Rivers.