Lucic hit Spacek from behind early in the second period Tuesday night, with the Montreal player going face-first into the glass. Spacek was bleeding and laid on the ice in obvious pain before he was attended to by a trainer and helped off. He later returned to the Canadiens' bench.
Lucic received a five-minute major for boarding and a game misconduct.
The two teams have a history of bad blood, most recently exemplified by Boston captain Zdeno Chara's hit on Max Pacioretty in a game in Montreal during the regular season. The Canadiens forward sustained a concussion and a cracked vertebra.