BOSTON -- Two days ago, Keith Tkachuk was playing for a team with no shot of making the playoffs. Now, he's in the midst of a playoff push and loving every minute of it.
Hossa snapped a 2-2 tie 7:28 into the third period when he took a drop pass from Belanger and fired a quick slap shot through a crowd and past Boston goalie Tim Thomas.
"I'm extremely happy to be playing with a guy like Hossa," Tkachuk said. "There's definitely a lot of skill here. It's a fun group of guys and it was fun to get a win in the first game."
Zhitnik and Tkachuk were acquired in separate trades this weekend.
Tkachuk had 20 goals and 23 assists in 61 games with St. Louis, and was considered the top player on the trade market. With the Blues 12 points out of playoff position, the 15-year veteran waived his no-trade clause.
Zhitnik, who had five goals and 19 assists in 61 games with the New York Islanders, had an assist.
"They are two huge additions," Boston coach Dave Lewis said. "Tkachuk with his status and his stature, his years and experience -- and I'm sure his hunger. On the back end, they got [Zhitnik] who can move the puck, plays hard, is smart and can be physical. I think they upgraded."
With the win, the Thrashers improved to 3-7-2 in February and pulled to a point behind Southeast Division leader Tampa Bay. Atlanta had lost six of seven entering the game to tumble from first place in its division to sixth in the tightly bunched Eastern Conference, with four teams battling for the final three playoff spots.
One of two franchises in the NHL (along with Columbus) never to make the postseason, the Thrashers hope their moves lead to a late playoff push.
"Our two new players played a strong game," Atlanta coach Bob Hartley said. "More importantly, it's a message from our owners that we mean business. The time is now to win some hockey games."
After Shean Donovan's 100th career goal gave the Bruins a quick 1-0 advantage, Zhitnik assisted on Mellanby's goal to tie it at 1 with 5:25 left in the first period.
The teams then traded goals before Hossa's game-winner.
Donovan and Brad Boyes each scored for Boston, which lost its second straight following a four-game winning streak.
Kari Lehtonen recovered from a shaky first period to save 22 shots, including six in the third period. He held the Bruins scoreless after the first period.
Thomas stopped 17 shots for the Bruins, who squandered leads of 1-0 and 2-0 to remain tied for 11th in the Eastern Conference.
"We're in a dog fight in the conference," Boyes said. "Playing a team like Atlanta, we have to take two points and try to take two points away from them. To give that team points just puts us behind a little bit more."
Atlanta committed just one penalty through two periods, taking advantage of four Boston penalties with a pair of power-play goals in those periods. ... Atlanta plays 11 of its last 17 games at home. ... Boyes extended his point streak to five games. He has four goals and three assists during that span. ... Boston outshot Atlanta 24-20. ... Atlanta is 3-0 against Boston this year.