The big forward sent Boston Bruins defenseman Johnny Boychuk to the hospital with a first-period check into the boards Thursday night, then scored the go-ahead goal in the second during Montreal's 2-1 victory.
Pacioretty's ninth goal in the last nine games helped the Canadiens stretch their unbeaten run to nine games (8-0-1). It also put Montreal (18-9-3) in first place in the Atlantic Division, a point ahead of Boston (18-8-2), which has two games in hand.
Pacioretty, however, wasn't smiling.
''It wasn't really a strong game for me,'' he said. ''I got the life sucked out of me when that injury happened. I just felt awful.''
Only 4:28 into the first meeting of the season between these bitter rivals, Pacioretty checked Boychuk into the end boards in the Montreal zone. Boychuk went face first into the top of the boards and fell to the ice.
He was on his knees, taking heavy breaths, for several minutes before trainers and medical staff got him onto a stretcher and wheeled him off the ice.
After the game, Bruins coach Claude Julien said Boychuk was released from the hospital and would travel with the team back to Boston. Julien had no details about the injury, which Bruins players said appeared to be a back problem.
The hit wasn't hard, but it was somewhat from behind. Pacioretty was given 2 minutes for boarding, which both teams felt was the right call.
''I felt terrible about it because I didn't really know what happened,'' Pacioretty said. ''I was just battling for the puck. I've been in that situation before. I had no intent to injure anybody.''
The Bruins seemed to agree, and none of them rushed to seek vengeance as is often the case when a teammate gets hurt. The injury quieted the Bell Centre crowd and took some steam out of the play on the ice for the rest of the period.
''I think they gave me the benefit of the doubt,'' Pacioretty said.
And the Canadiens, outshot 10-3 in the opening period and down 1-0 on a goal by Gregory Campbell, jumped on Boston in the second with an 18-7 shots advantage and goals from Tomas Plekanec and Pacioretty.
Boston had not played since Saturday, while Montreal was coming off a 4-3 shootout win Wednesday night in New Jersey. The Canadiens were playing their third game in four nights and sixth in nine nights, but they weren't easy pickings for the Bruins.
''The second period was atrocious,'' Julien said. ''It was unacceptable.
''There are no excuses about playing with five defensemen. We have to look in the mirror.''
Boston got the first goal at the 17:35 mark. Andrei Markov cleared the puck to the Boston blue line, where Dennis Seidenberg kicked it forward, sending Milan Lucic in on a 2-on-1 break. The big wing slipped a pass to Campbell for a shot into an open side.
Plekanec tied it 9:16 into the second when he beat Rask from a tight angle with a medium-speed wrist shot.
A burst of speed from Brendan Gallagher caused confusion in the Boston defense and Pacioretty backhanded Raphael Diaz's rebound in from the slot at 17:42. Pacioretty's last nine goals have all come in five games on home ice.
''The first one was off to the side of the net and I gave (Plekanec) too much net to shoot at,'' Rask said. ''The second was a high rebound and he scored.
''But if you look at how we played in the second period, you can't be happy with that.''
Montreal has beaten Boston four straight times dating to last season.
''I'm proud of my players,'' said Canadiens coach Michel Therrien, whose team plays again Saturday night at home against Buffalo. ''Even if we had a slow start, we adjusted well in the second period.
''My players emptied the tank and they were rewarded.''
The teams meet again Jan. 30 in Boston.
NOTES: Montreal dressed Douglas Murray and George Parros, and sat Francis Bouillon and Ryan White, who both played Wednesday in New Jersey. Rene Bourque remains sidelined with an upper-body injury. ... Parros got his first shot on goal in seven games with the Canadiens. ... Adam McQuaid (lower body) was out for Boston, while Jordan Caron and Kevan Miller were healthy scratches. ... As in other NHL rinks, a moment of silence was held for Nelson Mandela.