Lucic, who has two assists and 24 penalties in the first two games of this best-of-7 series, will miss Monday's Game 3 at the Bell Centre. Boston leads the series, two games to none.
On the incident in question, Lucic struck Maxim Lapierre in the head with his stick during a scrum in front of Montreal goalie Jaroslav Halak with 4:32 remaining in Game 2.
The incident began with Lucic and Montreal defenseman Mathieu Schneider in a pushing match with their sticks, earning Lucic a cross-checking penalty and Schneider a high-sticking infraction.
Montreal's Maxim Lapierre quickly joined the fracas and Lucic hit the Montreal forward in the face with his stick, earning a match penalty under Rule 60.4, which mandates the call when "a player or goaltender attempts to or deliberately injures an opponent while carrying or holding any part of his stick above the shoulders of the opponent."
"While it is unclear whether Lucic's glove or stick makes contact with Lapierre, what is clear is that he delivered a reckless and forceful blow to the head of his opponent," said NHL Senior Executive Vice President of Hockey Operations Colin Campbell.
A hearing, conducted by phone, was held Sunday afternoon before the Bruins departed for Montreal in preparation of Monday night's Game 3.
Before the suspension was announced, Claude Julien said he would dress rugged forward Byron Bitz in his place. Bitz, a rookie, would likely play on the fourth line with Stephane Yelle and Shawn Thornton, while current fourth-liner Blake Wheeler would move up to Lucic's spot as the left wing on the second line with center Dave Krejci and winger Michael Ryder.
With the injury to matt Hunwick before Game 2 forcing reserve Shane Hnidy into the lineup and with defenseman Andrew Ference still on the mend, Boston will have no reserves if Bitz dresses Monday.
That means the team will likely have to make a call-up or two from Providence before Monday's game. Providence plays Game 3 of its first-round matchup of the Calder Cup playoffs Sunday night.