That's according to Stephen Jackson, who scored 27 points while Harrington added 20 to help the Pacers beat the Hawks 100-90 on Friday night in their first meeting of the season.
The two former Hawks led the Pacers to their second straight win and fourth in five games. Jermaine O'Neal added 16 points for Indiana.
"I'm glad he's (Harrington) with us. He beat us all by himself last year," said Jackson of Harrington, who signed as a free agent with the Pacers during the summer after two seasons with Atlanta.
"It seems like he must be the difference maker," Jackson said.
"It was fun to come back to Atlanta," Harrington said. "I was like a kid when I saw all those guys (Hawks) before the game. We just wanted to get back on a winning streak."
Joe Johnson had 31 points for Atlanta. The Hawks have lost three straight and seven of eight.
"Give those guys, (Jackson and Harrington) credit, they played great but that's not the reason we lost. We just acted like we didn't want to play," Johnson said. "Like we're just going through the motions. It shouldn't be that way. We're professionals. We shouldn't have to beg guys to play every night."
Jackson scored 16 points in the first half to lead the Pacers to a 52-47 advantage. Johnson had 22 first-half points for the Hawks, whose only lead was at 2-0.
Indiana built a 16-point lead at 100-84 with just over a minute to play.
The Hawks stayed close until Harrington got hot midway through the third period.
Leading 55-52, Harrington scored nine of Indiana's 11 points in a 4-minute span to give the Pacers a 66-56 lead with 5:45 left in the period and the Hawks never got closer than eight points the rest of the way. Atlanta trailed 80-69 entering the final period, unlike the Hawks' last two losses.
Atlanta blew a 21-point fourth quarter lead Wednesday night in losing 112-106 to Utah. The Hawks also lost a 12-point fourth-quarter lead in their previous game, a 106-104 overtime loss on Saturday to Chicago.
Jeff Foster scored only three points for Indiana, but had 16 rebounds. Jamaal Tinsley added 10 points and nine assists. Atlanta's Zaza Pachulia had 10 points and 14 rebounds.
Hawks G Josh Childress hoped to return from a left foot sprain, but the third-year player missed his 18th straight game. G Tyronn Lue was out for the third straight game due to a strained groin. ... Harrington, who played the previous two seasons with Atlanta after six years with Indiana, made his first appearance of the season against his former Hawks teammates. ... Pacers C David Harrison missed his fifth consecutive game with an injured left shoulder.