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 left, 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.

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

“We would like to get 1 or 2,” Boston Coach Doc Rivers said of the top two seeds.

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. 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 one point and one rebound in 15 minutes.

Rivers said he was forced to play O’Neal against the Hawks after Nenad Krstic hurt his right knee 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 and finished with 15 points and 10 rebounds.

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

“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.”

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.