We’re just a week into Training Camp and reality is starting to hit hard for the Bruins blue-line as they prepare for the start of the 2015-16 regular season.

They’ll be preparing without Dennis Seidenberg.

On Wednesday, the Bruins announced that the German defenseman will undergo back surgery and miss approximately eight weeks.

Although he struggled throughout the 2014-15 season — a year after a torn ACL ended his 2013-14 season — there’s no denying Seidenberg’s importance to the Black and Gold. The Bruins were hoping to get a bounce back season from Seidenberg in a year of transition, and now they’ll have to wait to get something out of him.

Seidenberg’s void opens up another spot on the Bruins D as youngsters like Colin Miller, Joe Morrow, Zach Trotman and Matt Irwin look to crack the opening night roster in a couple of weeks. Replacing his contributions as a top-four defender will be a challenge, however.

“Well it’s definitely a setback first and foremost from Dennis’s standpoint,” GM Don Sweeney said to reporters regarding Seidenberg’s injury. “You know he’s worked hard. He came back from an ACL last year and has a setback which we hope being identified fairly early in camp, tried to get some rest to let it calm down — wasn’t able to do that and you know got a couple weeks ahead of the season to have the surgery done and get the healing well underway. So it’s definitely a setback. I mean it’s obviously an opportunity for the other guys we were evaluating anyway, amongst our D core, and we’ll go from there.”

With Seidenberg’s injury, the only Bruin who has regularly played over 20 minutes a night on a yearly basis is Zdeno Chara. Though he may be a little past his prime, the presence of the 6-foot-9 captain is still intimidating for the opposition on the other side of the ice to address.

Still, Chara and the rest of the team will need even more contributions from the rest of the blue-line. Whether it’s Torey Krug wanting to earn a spot in the top-four, or Kevan Miller and Adam McQuaid being physical or Morrow, Irwin, Trotman or Colin Miller trying to make a good impression, each member of the B’s defense will have a lot on their plate as they try to establish a back-end presence that had their share of problems a year ago (but then again, who didn’t).

“Dennis Seidenberg is a real important part of our team, but we’ve played without him many times with injuries here,” head coach Claude Julien said to the press after Wednesday’s Training Camp sessions. “So I’m just more or less looking at doing what we need to do here with the guys that we have and not so much what I’m going to miss about him and that’s what am I going to get from the other guys that are going to be replacing him that’s most important.”

“It’s never good news when one of your teammates and one of our steady defenseman is going to be out for a period of time,” Chara added during his media scrum with the press.

“It’s a chance for other guys to really step up. We have some guys that have already been playing in the league for a number of years, so we need to make sure we stay on top of things, communicate and do whatever we can to support each other.”

Perhaps Colin Miller will impress the Bruins brass enough to earn a spot on the roster. Maybe Trotman and Morrow can make a smooth transition after spending last year between Boston and Providence and/or the addition of Irwin can turn out to be one of the more underrated signings by Sweeney this off-season.

The other option for Sweeney will have to look at the trade market in hopes of acquiring a defenseman to fill a critical need on the Black and Gold. (Dustin Byfuglien anyone?)

The one thing the Bruins did not need was an injury to one of their veteran defenseman to start training camp. Coming off a plethora of injuries last season, the Bruins can’t seem to shake off the bad karma they inherited over the last 12-plus months.