ATLANTA — The fact that the Celtics played so well in the second half — 67 points, nine 3-pointers, and 15 fast-break points — and still lost was a testament to how poorly they played in the first half.

The first 24 minutes of Game 1 of the Eastern Conference first-round series went much like the final two Boston games of the regular season. At halftime of their past three games, the Celtics have trailed by a total of 63 points. They lost one by 14, won the second, and lost Saturday, 102-101.

There is reason for optimism and encouragement after losing to the Hawks at Philips Arena. The Celtics figured something out defensively during the first half, began attacking the basket in the second half, and were a couple of missed open 3-pointers from stealing a victory.

The Celtics could have easily relented after another bad first half in which they shot 23.1 percent, missed 14 3-pointers, and did not score a fast-break point. Yet they rallied to begin the third quarter, forced Atlanta into several one-on-one freelance situations, and played with more poise.

There is still an opportunity to win this series but the Celtics have to use their two days off to reflect on their recent slow starts. And they also likely have to move on without Avery Bradley, who suffered a right hamstring strain and will have an MRI on Sunday, a test that will likely reveal a significant injury.

Boston has enough to beat Atlanta but it has to be tougher with the ball, stop fouling so often early in quarters, and begin hitting some 3-point shots. The team was exhausted following Game 1 but not broken.

“It’s encouraging but at the same time, that first half killed us,’’ forward Jae Crowder said. “We have just got to play way better from the start.’’

The Game 1 mistakes can be rectified. Of the 24 second-half minutes, the Hawks spent 16:45 in the bonus. Fouling early in quarters has been a season-long problem for the Celtics, but Crowder astutely said that if they are aggressive early in games, the officials may give them the benefit of the doubt throughout the game.

The team’s relationship with officials has been tenuous all season. Brad Stevens picked up his first technical foul in more than a year on Saturday. At one point in the fourth quarter, the Celtics had committed 27 fouls to Atlanta’s 15. Complaining is not a solution. But they do need to get a couple of more breaks.

In one key sequence with 1:33 left, Atlanta’s Al Horford missed a 20-footer, grabbed the offensive rebound while throwing two Celtics to the floor, appeared to travel as he spun to the basket, and then was fouled by Evan Turner, who told the officials to look at the big screen for the Horford travel.

Horford sank both free throws for a 96-91 lead.

“A couple of them were bonehead plays and a couple of them, it’s kind of hard to gauge, you know?’’ Turner said. “It’s two or three calls missed on that play but that kind of didn’t shock me in general, though. When it comes to loose-ball calls, it could go either way but when he just grabbed it and then did a spin, you can’t really miss that call. But that’s not what lost the game.

“I’m kind of over looking to the refs to help us. We need to do ourselves a favor and help ourselves.’’

The Celtics have two days off to lament their mistakes, get some positive practices in, and attempt to cure their early-game ills. Boston made perhaps double the mistakes of the Hawks. They played 95 percent of the game from behind and were forced to completely outplay their opponent just to make it competitive.

And they were able to take two fourth-quarter leads before wearing down in the last four minutes.

The Celtics were angrier with themselves than with the result. Stevens was rather chipper afterward, a sign that he sees a breakthrough approaching.

“I thought a lot of guys did a lot of good things to get back in that game, we’re going to have to knock down some more shots, obviously,’’ he said. “We just missed a lot of open ones. We struggled to guard them in the first six minutes but after that I thought we guarded them well the whole night.’’

The Hawks shot 38.7 percent following the first quarter but they were bailed out by the Celtics’ fouling and some defensive mismatches that allowed Jeff Teague to get to the basket against a slower defender in the fourth quarter.

Stevens will spend the next 48 hours breaking down the game tape, making some Game 2 adjustments such as a smaller lineup, more playing time for Marcus Smart, and more emphasis on punching first.

This was not a discouraging loss. If the Celtics had relented after a 17-point halftime deficit, then there would be reason for major concern. The Celtics returned to their old selves Saturday, but they need to show up to the party a little earlier and a little more prepared.

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.