ATLANTA - The Atlanta Hawks are looking more like a postseason contender again after a renewed commitment to defense delivered a second straight win over a playoff-bound team.

Al Horford capped his 35th double-double with a key tip-in with 7.9 seconds remaining, Jamal Crawford scored 20 points and the Hawks surged in the fourth quarter to beat the travel-weary Boston Celtics 88-83 on Friday night.

The Hawks' first win in three tries against Boston this season followed an 85-82 win over Orlando on Wednesday night, giving Atlanta four straight wins after losing 14 of 21.

"I've been waiting for this kind of quality effort," said Hawks coach Larry Drew, who stopped short of saying his team had completely recovered from its funk. "Certainly I see signs, but I'm not going to go out on a limb and say they're there."

The Celtics fell to third in the Eastern Conference, ½ game behind Miami and three games behind Chicago.

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"We would like to get 1 or 2," said Boston coach Doc Rivers.

Paul Pierce led Boston with 25 points. Rajon Rondo had 13 points and 10 rebounds, and Kevin Garnett had 10 points and 10 rebounds.

The Celtics arrived in Atlanta at 4 a.m. on Friday following Thursday night's 107-97 win at San Antonio. Boston's players appeared to tire late in the game after taking a 60-48 lead in the third quarter.

Boston's Jermaine O'Neal played for the second straight night after recovering from arthroscopic surgery on his left knee — his first action since January. He had only one point and one rebound in 15 minutes.

Rivers said he was forced to play O'Neal against the Hawks after backup center Nenad Krstic hurt his right knee on Thursday night. Krstic did not play against Atlanta.

Joe Johnson scored 19 points for the Hawks despite making only 4 of 20 shots from the field. Horford had 16 points and 15 rebounds.

Crawford, Johnson and Horford are familiar names in the Hawks' list of scoring leaders. The surprise was Zaza Pachulia, who led Atlanta with 10 points and six rebounds in the final 12 minutes to finish with 15 points and 10 rebounds.

The Hawks outscored the Celtics 26-15 in the final period as Drew stuck with the same five players, including Crawford and Pachulia.

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"I thought Zaza was the toughest dude on the floor and changed the whole game," Rivers said. "He was banging everybody, getting offensive rebounds, and I thought that was a great move by them."

Drew said Pachulia "just gave us some huge, huge minutes. ... I was not going to take him out of the game. He was a presence out there. We got into a rhythm when he came into the game, and we didn't want to interrupt that."

Starters Josh Smith and Marvin Williams sat out the final period. Smith said he couldn't argue with Drew's decision.

"I was one of the biggest cheerleaders out there," said Smith, who had only six points and four rebounds.

The Celtics have brought out the best in Pachulia since the 7-footer went nose to nose with Garnett in the 2008 playoffs.

"It's a special game for us, the organization and the fans," Pachulia said.

Garnett said playing two road games in two nights is not an excuse for the letdown.

"Back-to-back is part of the NBA," Garnett said. "It has been since I've been in the league, so that's no excuse. Either we can quit and go home or we can continue to get better. There's no history of quitting in this team, so we'll just move forward."

Rivers said one sign of fatigue was his players taking quick jump shots.

"The difference between last night and tonight was the ball didn't move enough," Rivers said. "I thought we took quick, bad shots."

The Hawks held a 17-8 rebounding advantage in the fourth quarter and a 52-38 edge for the game. Atlanta also outscored Boston 18-2 in second-chance points.

"We got absolutely crushed on the glass tonight," Rivers said.

Notes: Krstic will have an MRI on the knee in Boston on Saturday. ... Boston's Pierce and O'Neal and Atlanta's Pachulia drew technical fouls for two incidents in the first quarter. Pierce drew his technical following a brief altercation with Johnson. Pachulia and O'Neal had to be separated late in the period.