"It was important for us to establish the pace of the game early on and the guys came out and did a tremendous job," said Atlanta general manager and coach Don Waddell.
Lehtonen made 26 saves for his ninth career shutout, including an outstanding stop on a breakaway by Marco Sturm midway through the second period.
"Tonight we played the same that we did the other night, but now it is 5-0," said Lehtonen, referring to Thursday night's 5-3 loss at Florida in which the Panthers outshot the Panthers 41-29.
"It's a couple of breaks here and there. It was fun to see it go this way," said Lehtonen. "The guys played great in front of me. Usually, when it's 5-0 after the second period, there will be some letdown."
Atlanta, which had lost two in a row after winning four straight, jumped on Boston early, scoring goals 1:32 apart. Kozlov scored at 7:50 on a pass from Eric Perrin, easily beating Boston goaltender Alex Auld from in close. The Thrashers made it 2-0 on Holik's fourth goal, with Andrew Ference defending the net after Auld got tangled up trying to clear the puck along the boards. Dupuis earned an assist.
The Thrashers' third goal came when Dupuis came from behind the net and tucked the puck past Auld at 16:45.
Auld was replaced by Tim Thomas at the start of the second period.
"We are all trying to turn this around. Obviously you want to do what you can to help your team get a win. It wasn't enough tonight. We have to stay together. We can't get frustrated," Auld said.
Kovalchuk got his ninth power-play goal at 11:05 of the middle period and then assisted on Zhitnik's goal 2:43 later for a 5-0 lead.
- There were two fights in the opening 2:30. The Thrashers' Chris Thorburn and Boston's Shawn Reich each got five-minute fighting penalties after 2:26. Four seconds later, Atlanta's Eric Boulton and Thornton went.
- Atlanta rookie F Colin Stuart, recalled Friday from Chicago (AHL), made his NHL debut and got his first point, an assist on Dupuis' goal. His brother, Mark Stuart, plays for Boston.
- The Thrashers had a crowd of 18,514, their fourth sellout.