BOSTON -- There’s a chink in the armor.

That doesn’t bode well for the Boston Bruins.

For a team built on defense, it’s alarming that the Bruins uncharacteristically have suffered numerous breakdowns this season. It continued Tuesday as the Minnesota Wild scored three unanswered goals in the third period en route to a 4-3 come-from-behind victory at TD Garden.

It would be easy to blame the absence of captain Zdeno Chara, who will be sidelined four to six weeks with a torn ligament in his left knee, for the defensive deficiencies, but the veteran defenseman has missed only two games since he suffered the injury this past Thursday. The breakdowns have been occurring all season.

“The offense has been good. The power play’s been great,” said Bruins goaltender Tuukka Rask, who faced a season-high 42 shots Tuesday. “We’re really driving the net and crashing the net, but then it doesn’t really matter when the defensive side of your game is the one that gets the worst out of that, so we have to be well-balanced in the future.”

Rask has never played with this type of lackadaisical defense in front of him during his career in Boston. Sure, it happens from time to time, but never to this extent.

“This season it’s been more than ever before,” he said of the breakdowns.

Poor defensive positioning, losing puck battles in front of the net and allowing opponents to get sticks on loose pucks have been far too common in front of Rask.

Rask’s job is to focus on the puck, and he should not have to worry if there’s a man open on the off post or in the slot. He should be able to trust his defensemen are doing their jobs. The last thing Rask needs is to lose his focus and start thinking about the possibility of an opponent being open.

“That’s kind of alarming a little bit,” Rask said of the mistakes in front. “It’s really simple. It all comes down to protecting the house, collapsing down low and keeping the [opposition] outside. As goalies, we like to expect that we make those saves when they come from the outside, and maybe even the second save, but when pucks end up behind us and guys are banging in loose pucks, it makes it difficult.”

The breakdowns can’t be blamed solely on the defensemen. When forwards don’t win puck battles along the walls and can’t successfully break out of the zone, it can cause chaos. That was the case against the Wild.

In the first 11 games of the season, the Bruins have allowed a total of 320 shots and have a 5-6-0 record. At the start of the 2013-14 season, with a completely healthy defense, the Bruins allowed 313 shots and jumped out to a 7-4-0 record. Any goalie and any coach will tell you it’s not about how many shots you allow; it’s about minimizing the quality chances and clearing out the traffic in front.

“The way mistakes are happening for us sometimes is unacceptable,” Rask said. “We really have to be better in front of our net. Way too many goals have been scored right there. We’ve talked about it, but it’s just not good enough right now. The 40 shots I’m not too worried about -- it’s the style [in which] we give them up that is pretty bad sometimes.”

When the Bruins are at their best, the solid defense leads to a quality offense. But that hasn’t been the case so far this season. Boston needs to tighten up its own end as an entire five-man unit, close off passing lanes, work harder along the boards and have better breakouts with crisper passes.

“That’s how we’ve always been, but lately, that hasn’t been the case," Rask said. "It’s been costing us."

The Bruins entered the third period Tuesday night with a 3-0-0 record this season when leading by two goals. In fact, Boston routinely has been the better team in the third period since the start of the 2010-11 season and has a 136-7-6 record when leading by two goals.

That changed against the Wild.

“It’s the worst lead in hockey, right? That’s what they say,” Rask said. “You let up, even for a minute, [and] bad things can happen. We take that penalty (Brad Marchand for holding) early in the third, and they took the momentum. Then they kept it for the next 10 minutes and got a couple of goals out of it. It evened out after that, and a bad bounce ends up costing us the game.”

Not having Chara and fellow defenseman Kevan Miller (shoulder) in the lineup for the foreseeable future will have a negative effect on the Bruins. But others simply need to play better.

Dougie Hamilton logged 28:32 of ice time Tuesday, which was a career high. Partner Dennis Seidenberg played 24 minutes. With the game on the line, Bruins coach Claude Julien was forced to shorten his bench. Matt Bartkowski played less than two minutes in the third period and finished with a total 8:56 of ice time.

So many times since he’s been the No. 1 goalie in Boston, Rask has bailed out his teammates. They are not reciprocating so far this season, and if this trend continues, Rask could lose his typical, calm off-ice demeanor. He only wants one thing right now.

“Taking care [of the area] in front of your net is not something new,” he said. “Whoever comes here should be capable of doing it, and lately we haven’t been doing that.”