Davis then signaled Rondo’s ejection, a few feet from the Celtics’ bench. Rivers lowered his head, clearly realizing Rondo had crossed the line.

Davis apparently ruled Bass had fouled Smith before the travel. Rondo reacted by disputing the decision. Davis signaled a technical foul on Rondo, turning toward the scorer’s table.

Then, Bass went down and briefly tied up the ball. Smith rolled away from Bass, who made another attempt to reach for the ball, his arm making contact with Smith’s head.

This is how the sequence went: Johnson lost control of his dribble as he attempted to back into the lane, Kevin Garnett diving to the floor to prevent Smith from gaining possession.

The tension was building as the Celtics cut an 8-point deficit to 78-74 in the final minute. But Josh Smith drew Brandon Bass’s sixth personal foul and Rondo clashed with Davis with 41 seconds remaining.

“I just think they get heated and I thought [Rondo] was more upset on the missed call on the play before, on the out-of-bounds play. I thought that started it.’’

“Well, they ran into each other, there’s no doubt about it. I thought it was a bump. I still don’t think it was intentional.

“I really hadn’t looked at the tape when I talked [Sunday],’’ Rivers said before the Celtics’ workout at Georgia Institute of Technology. “I was going on my vision. I have looked at the tape 10 times now.’’

The punishment could well have been two games; Rondo was banned for two games after he tossed a ball at a referee in Detroit in February.

Coach Doc Rivers and Rondo both said after the game the contact was unintentional. Rondo made his case in a telephone interview Monday morning, and the league handed down the minimum sentence.

According to the NBA rulebook, “Any player or coach guilty of intentional physical contact with an official shall automatically be suspended without pay for one game. A fine and/or longer period of suspension will result if circumstances so dictate.’’

Rondo clearly made contact with official Marc Davis in the final minute of the Celtics’ 83-74 loss Sunday night, but the league’s decision to suspend him for one game had to be made on the question of intent.

There was little question the NBA would suspend Rondo for Tuesday’s Game 2 against the Hawks, but a real possibility of harsher judgment remained.

ATLANTA - The Celtics’ lobbying efforts for Rajon Rondo might have paid off Monday.

“You know, it’s funny, actually I told Brandon when I watched it live, I thought it was a foul, and Marc made the right call,’’ Rivers said. “And, then, when I watched it, I apologized to [Bass] and said it was a jump ball.

“Having said all that, we’ve got to control our emotions, there’s no doubt about that. We talked about that two days ago as a team.

“I rarely have those type of meetings and now I’m wishing I hadn’t - maybe nothing would’ve happened.’’

Rondo’s frustration had apparently been building since the opening quarter. The Celtics started poorly and fell behind by 19 points in the second quarter. The Hawks forced the Celtics out of their comfort zone.

The Celtics finally found an offensive flow in the second half. They upped their intensity level and appeared capable of a stunning comeback. The Celtics trailed, 76-70, when Paul Pierce missed a 3-pointer with 2:14 left, Rondo believing he had retained possession as he battled Smith for the long rebound.

Rondo did not receive that call and, 16 seconds later, Jeff Teague drove for a 78-70 Hawk advantage.

Garnett and Pierce pulled the Celtics within 78-74 with 1:01 left, then Bass fouled out and Rondo’s frustration spilled over.

“It’s part of the package with our team, we’re a volatile team in a lot of ways,’’ Rivers said. “Rondo’s an emotional player and, you know, we say you have to kindle a fire to start one - and I like his fire. But sometimes it burns you, you know what I mean?

“He’s into the game, he’s a fighter for his team. But we didn’t want him to go that far, obviously. That’s just who he is. That’s also what makes him great. So it’s that fine line that you’ve got to walk and every once in a while he crosses it.’’

In a statement, Rivers said, “Obviously, from a competitive standpoint, we are disappointed with the league’s decision to suspend Rondo. He plays a valuable part in our team’s success. We accept the punishment and will use it as a learning tool for our players.’’

Before the suspension was announced, Rivers talked as if he knew it was coming. “I hate to say it, when security calls they’re not usually calling you to give you money,’’ Rivers said. “If I have one issue with the league, that’s it, they wait until after shootaround and we’re guessing. I’d like to know right now.’’

Rivers plans to make certain the Celtics do not repeat Sunday’s lethargic start.

“We’re going to be ready to play basketball when they tip it off tomorrow.’’

Frank Dell’Apa can be reached at f_dellapa@globe.com.

© Copyright 2012 Globe Newspaper Company.