The Bruins sit atop the NHL standings with a 12-1-2 record as we inch our way toward Thanksgiving. Given all their key personnel losses, it is stunning they are just a point off the pace they set last year in their record-breaking 65-win season.

While many undoubtedly thought at this point last season their success rate was unsustainable – and then proven wrong – this year’s rate of winning seems even less likely to continue without some marked improvement in their defensive game.

The B’s are often giving up as many — if not more – high-danger chances than their opponents.

The good news is they’ve had the goaltending from Jeremy Swayman (.944 save percentage, 1.69 GAA) and Linus Ullmark (.928 save percentage, 2.23 GAA) to cover up those blemishes. The bad news is they are simply overly reliant on their goaltending to be tremendous every night with what they’re able to create offensively. They have yet to win a game in which their opponent has scored more than two goals.

Coach Jim Montgomery has identified one of the big culprits as being their rush defense. He’s talked about it for much of the season, including after their most lopsided win in Buffalo on Tuesday. Though the scoreboard read as a 5-2 blowout, Natural Stat Trick had the teams even in high danger chances at nine apiece.

Montgomery was wary of this as far back as the summer when he knew he’d be losing three centermen (Patrice Bergeron, David Krejci and Tomas Nosek) who were well schooled in the B’s defensive system that relies so heavily on its pivots.

After Wednesday’s practice, Montgomery outlined how the team can improve in the area.

“It all starts in the offensive zone and the consistency of having (a third forechecker) on the strong side of the puck so that if things go awry — and you are going to lose possession, it’s a game of turnovers – then you have balance,” said Montgomery. “It’s the D-men understanding when they can press up to hold the puck in the offensive zone in relation with that F3. That’s where it really starts. And then our two forwards who are low, they can’t get beat up the ice by people. Then when you get into the neutral zone and we just think, if they have possession, you can’t lose two people outside, because then the 3-on-3 or the 2-on-2 becomes a 2-on-1. We want to force plays by our blue line … it’s everybody working together. It’s more of a work progress than it was last year, but we had centers that had played a combined 35 years in the league last year. It’s just normal.”

Through 15 games, the B’s have allowed 127 high danger chances (ranked 13th in the league) while creating 135 (ranked 16th). Montgomery said most of those chances are coming off the rush.

“We’ve given up more in the D-zone, but it really starts because we don’t kill plays as often as we used to, so we spend more time in our D-zone,” said Montgomery. “It’s a little bit of a combination. But for us, the area of concern more – by a lot – is rush defense.”

Pasta cookin’

One reason beyond the goaltending for the B’s coming out on top on most nights is the consistent production from alternate captain David Pastrnak. After his three-point night in Buffalo (1-2-3), he’s one point behind Vancouver’s Elias Petterson going into Wednesday’s games for the league lead in points and, with 11 goals, he’s two off the league lead.

Given he’s had to adapt to a left-handed centerman in Pavel Zacha for the first time in his NHL career – he’d played primarily with righties Patrice Bergeron and David Krejci – his continued production is noteworthy.

“I don’t know who I was saying this to on the plane (from Buffalo), I think it was (GM) Don Sweeney, I thought that he would have a harder time producing without Bergy and obviously without Krech to work with,” said Montgomery. “But I do know that in my year-end meeting with him, I said, ‘There’s going to be a lot more put on you next year’ because we figured they were moving on. He just looked at me and said, ‘Yeah, I’m expecting it. Don’t worry about it.’ That’s what he said to me. Now I don’t worry about it. He’s become more of a puck possession guy, and I think he realized that.”

Defense to offense

The B’s received two goals from defensemen on Tuesday, but Montgomery wants to see his blueliners even more shot-minded than they have been. If there are forwards at the net, pound away, he said.

“When there’s traffic at the net, and I think we have a team that’s doing a really good job this year by our forwards getting traffic at the net, the D-men need to be more selfish,” said Montgomery. “It’s not because they don’t want to score goals, it’s just that we need to create more consistent habits of getting pucks to the net.”

Injury updates

Matt Grzelcyk (upper body) is eligible to come off LTIR for the B’s game against the Rangers in New York on Nov. 25 and Montgomery expects him to be ready for that game. That gives rookie Mason Lohrei four more games to make the club’s decision to send him back to Providence that much more difficult. If that decision was upon them now, then the guess here is that he’d be going to back to the AHL to play 20-25 minutes a night in all situations. … The coach said Morgan Geekie (upper body) is “at best” a week away. … There’s no timeline on Milan Lucic (lower body).