On Sunday, the Thrashers (31-23-10) pulled off one of the biggest deals ahead of Tuesday afternoon's trading deadline by acquiring Tkachuk from St. Louis for center Glen Metropolit and three draft picks including a 2007 first-round selection.
Tkachuk, who was second on the Blues in scoring with 20 goals and also has 23 assists, joins a team that has high-scoring wings Marian Hossa, Slava Kozlov and Ilya Kovalchuk but hasn't had a top center since Marc Savard left to sign with Boston (30-27-4) as a free agent last summer.
"My game is pretty simple," said Tkachuk, an eight-time 30-goal scorer. "When you're playing with guys like that, you know the puck is eventually going to be at the net. My job is to be at the net and try to get those garbage goals."
Tkachuk, who can become an unrestricted free agent July 1, isn't the only newcomer to the Thrashers' lineup. Following Saturday's 4-1 loss to Carolina, Atlanta picked up Zhitnik from Philadelphia for former first-round pick Braydon Coburn. A 14-year veteran defenseman, Zhitnik lends playoff experience, having appeared in 94 postseason games including two Stanley Cup finals -- with Los Angeles in 1993 and Buffalo in 1998.
"Over the years, we've always been pretty conservative when it comes to trading away picks or prospects. We've always protected the future. Well, the future for us is now," said Don Waddell, the Thrashers' only general manager since the team entered the league in 1999.
On Jan. 28, Atlanta had 64 points and was atop the Southeast Division with a six-point lead over Carolina and a 10-point edge on Tampa Bay -- the last two Stanley Cup winners. In 13 games since, Atlanta has gone just 3-8-2. With 72 points, the Thrashers are now three in back of the first-place Lightning and only one ahead of the Hurricanes.
"This is crunch time, there's no question about it," said Tkachuk, whose new team is sixth in the Eastern Conference. "This is a big move by Atlanta. They're putting in on the line with me coming there. I expect to go in there and do the right things on and off the ice. We just want to get in the playoffs. Once you get in the playoffs, anything can happen."
Boston, meanwhile, has 64 points and is tied with the New York Rangers for 11th in the East. Both teams are six points behind the New York Islanders and Montreal for the eighth and final playoff berth in the conference.
The Bruins' bid for their first five-game winning streak since 2004 ended Saturday night with a 7-2 loss to Florida. Trailing 5-0, Boston got power-play goals 48 seconds apart from Savard and Brad Boyes in the second period, but goaltenders Tim Thomas and Hannu Toivonen combined to face a season-high 52 shots as the Bruins were swept in the four-game season series.
"We didn't defend well enough and we didn't generate much offense," Boston coach Dave Lewis said. "Only when we had the power play did we have some quality, quality chances."
Boston may be without rookie center Phil Kessel for this game after he suffered a lower-body injury in the loss. Kessel missed a month earlier this season after undergoing treatment for testicular cancer.
The Bruins have lost both matchups with the Thrashers this season in Atlanta, but are 4-0-1 with a tie in the teams' last six meetings at TD Banknorth Garden.