If there’s one thing you could criticize the Bruins for this year, it’s their lack of killer instinct. And last night at the First Niagara Center, it finally came back to haunt them.

The B’s were dominating in the second period but could not deliver the knockout blow, and, after taking a one-goal lead into the third, they saw it quickly go up in smoke. The struggling Buffalo Sabres scored three unanswered goals to beat the B’s, 4-2, for just their second regulation loss of the season, both to Buffalo.

“I think we won here last time with a 2-1 lead and we’ve protected the lead pretty well in the past,” said Rich Peverley, one of the two Bruins goalscorers, “but maybe that’s something we’ve been hanging our hats on too much lately, and we have to go out and do it.”

The B’s have won 8-of-12 games this year and, for the most part, it’s been good times all around. But they have not held a lead of more than two goals at any point in the season and, more often than not, the margin for error has been far too thin. While they’ve dominated territorially in most games, they haven’t scored the goals that would match that domination.

Tyler Seguin has just one non-empty net goal, Milan Lucic has just two of the same, Patrice Bergeron also has just a pair, Nathan Horton has missed on some good chances and, with Peverley’s tally last night, the third line has produced just three goals all year.

While Sabres goalie Ryan Miller (30 saves) had something to do with the B’s frustration, coach Claude Julien bemoaned the missed opportunities.

“We’ve got some goalscorers who are not producing, and when they’re not producing, it makes it tough,” Julien said. “And when you had the opportunities we had, especially in that second period, there was no way it should have been a 2-1 hockey game. We went into the third period probably overconfident. You like your team to be confident, but not overconfident. We came out in the third and forgot to do the work.