BOSTON - On Friday morning, General Manager Peter Chiarelli announced to reporters at TD Garden that defenseman Zdeno Chara will be out 4-6 weeks with a tear in the posterior cruciate ligament of his left knee.

Chara suffered the injury at 11:15 into the first period of Thursday night's game against the New York Islanders at the Garden, when he landed a heavy hit that knocked down John Tavares at the top of the left circle in the defensive zone.

"This is completely different, separate, isolated from the other ligaments that are more critical in the maneuvering of the knee, so good news is, it's isolated to that ligament [in the back of his left knee]," Chiarelli told media during the press conference.

"Bad news is he's out 4-6 weeks. Might be a little earlier than four weeks, but a conservative time frame would be 4-6 weeks."

The loss of the towering 6-foot-9, six-time Norris Trophy Finalist and backbone of the Bruins' defense will affect every aspect of Boston's game.

"Well, it's obviously a blow," said Chiarelli. "He's one of the premier defensemen in the League, but I'd rather have it 4-6 weeks than 4-6 months."

The good news is that as of right now, Chara will not require surgery for his recovery.

"Right now, it's not a likely option," said Chiarelli. "But as you said, anything can happen. Anything can happen with anything, so I mean, I can't give you a 100 percent statement, confirmation, really on any injury."

Chara's knee will have to be immobile, but he can continue to work out the rest of his body. The Bruins are hoping his recovery time frame remains around that one month marker.

"Four to six weeks. We'll have him back," said Chiarelli, amidst his response to a reporter asking if the Bruins would look outside the organization for help.

"You know, I don't normally comment on that stuff. I know I have on the forward side of it, and I'll leave it at that. You guys can speculate," the GM told reporters.

Until 'Big Zee' returns, the Bruins will have to step up, on and off the ice, in all situations.

In the short term, Boston recalled blueliners Zach Trotman and Joe Morrow from Providence Friday morning on an emergency basis. They'll join Dennis Seidenberg, Dougie Hamilton, Torey Krug, Adam McQuaid and Matt Bartkowski in picking up the slack. Kevan Miller remains out indefinitely with his dislocated right shoulder.

But stepping up won't just apply to the Bruins' defenders. It's going to take an entire team effort.

"You hope everyone else picks up the slack," Chiarelli said. "We had a stretch before - it might not have been the same about of time - where Zee was out. They don't happen too often."

Chara has only missed one game due to injury in the past three seasons (2012-15).

"You hope everyone picks up the slack and we play a solid defensive game."