A off-night for Paul Pierce (3 for 12 from the field), plus the Celtics’ tendency to sabotage themselves, led to a dramatic finish, although the Celtics were still able to take a 2-1 lead in their first-round playoff series.

Rondo, returning after a one-game suspension, produced his seventh career playoff triple-double (17 points, 14 rebounds, 12 assists). Allen, in his first appearance after an 11-game absence because of bone spurs in his right ankle, went for 13 points and six rebounds in 36 minutes 51 seconds.

Allen and Rondo made key contributions in overtime after the Celtics had squandered an 11-point fourth-quarter advantage.

“It wasn’t pretty, but who said it had to be pretty?’’ Pierce said.

The Hawks, missing power forward Josh Smith and two centers, were able to stay in contention by shuffling lineups and isolating Joe Johnson (29 points) in half-court sets. Atlanta’s small lineup became even more effective after the Celtics lost Avery Bradley to a left shoulder injury in the third quarter.

Bradley’s injury is not considered serious and he is expected to play in Game 4 Sunday, according to a league source.

“We knew they were going to go small, but it still was quirky and it bothered us a little bit,’’ Celtics coach Doc Rivers said. “They just fought. And, I thought early on, they were playing free, loose, and almost with more intensity. And I thought we kind of, we joined in, as well.’’

After a jumper by Kevin Garnett (20 points, 13 rebounds) upped the advantage to 76-65 with 6:59 remaining, the Celtics seemed ready to coast to the finish.

But the Celtics lost their offensive compass after taking an 80-72 advantage with 4:04 remaining. Rivers called it “milking the clock - you can do that when the other team has two ‘bigs.’ But when the other team has five guards on the floor, you absolutely can’t do that.’’

As the Hawks closed, Rivers was forced to extend starters’ minutes and sweat things out. Garnett played 42 minutes, one more than his high this season. Pierce played 47 minutes, and all 29 minutes after halftime. Rondo played 49 minutes, but also missed 15 of 22 field goal attempts and had six turnovers.

“Too many minutes - I got stuck with Kevin, honestly,’’ Rivers said. “Usually we take him out at the six-minute mark in the fourth. That was right when we were starting to make a push - and with Rondo. So, we took the gamble. And it backfired.’’

Rondo got the lead to 80-72 with a lefthanded drive with 4:04 remaining. Then Rondo grabbed three rebounds in a 15-second span, one off his own miss, to achieve the triple-double. But Rondo’s airball drive led to a Willie Green 3-pointer in transition as the Hawks pulled within 5 with 2:32 to play. Johnson tied the score with 5 points in a 25-second span, including a 3-pointer after a Pierce offensive foul.

The Celtics finally were able to clamp down on Johnson with a Pierce-Mickael Pietrus double team on Atlanta’s final regulation-time possession, leading to a Green miss with 14.9 seconds on the clock. Pierce missed a buzzer jumper, sending the contest into overtime.

“I was really worried going into the overtime,’’ Rivers said. “Just looking at Paul, Kevin, and Rondo. They didn’t look that fresh. And, honestly, I looked at the other team – they looked pretty bad, too, so that made me feel a little bit better.’’

Rondo scored on a drive 15 seconds into overtime and Green kept the Hawks even with a third-chance follow. Rondo made it 84-82 with a back-in on Teague with :02 on the shot clock, but then missed a layup off a steal.

Pierce upped the lead to 4 points with 2:45 remaining. The Celtics had possession with a chance for a 6-point edge, but Allen airballed a 3-point try at the shot-clock buzzer and Johnson scored on a drive, the final Hawk points of the night.

Rondo banged a 20-footer off the backboard at the shot-clock buzzer before Johnson’s pull-up fell short. Garnett dunked off a Rondo miss out of a timeout to restore the Celtics’ 4-point lead with 28.1 seconds on the clock.

Johnson launched a 3-pointer out of a timeout, Allen rebounding and converting a free throw with 21.4 on the clock.

“We’re giving them the day off [Saturday] because they’re exhausted,’’ Rivers said. “And I don’t want Ray in the gym because he would do something, he would shoot, or something. So, that’s unusual for us to take a day off in the playoffs. But they need one.’’

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