As many in The Hub of Hockey recall, the Bruins set some fireworks of their own on July 4 when they sent Tyler Seguin to the Dallas Stars. Two months later, the details of that trade were well-documented in the new all-access series “Behind the B”.

If anything, the trade proved one thing in the Bruins’ locker room: that anyone is expendable in the Salary Cap era.

“It came as a bit of a shock,” said forward Brad Marchand, a former linemate of Seguin’s. “I think there’s some guys who thought that we were pretty safe and it was a bit of a wake up call. Everyday you come in, you need to make sure that you’re doing everything that you have to do to stay here. And I don’t think anyone expected Segs to be shipped up that early, but it took awhile for it to sink in, and he’s a pretty young player, and you have to wish him the best.”

Perhaps Seguin, along with Rich Peverley, will find their groove again in Dallas.

On the other hand, the Bruins made out fairly well in that trade: acquiring 28-year old Loui Eriksson as one of their pieces. In seven seasons with Dallas, the Swedish forward compiled 357 points (150 goals, 207 assists) in 501 career games, and posted three consecutive 70-plus point seasons from 2009-2012, including a career-high 73 point campaign in 2010-11.

Defensively, Eriksson has also shined, and for that he is paired with Marchand and another two-way forward, Patrice Bergeron. The trio made their debut in the first session of training camp Thursday morning at the TD Garden.

There’s still some kinks that the Marchand-Bergeron-Eriksson line need to work on, including the chemistry between the three, before the Bruins open the regular season in three weeks against the Tampa Bay Lightning. But day one of training camp was a small glimpse of things to come.

“I think we’re all smart players, and we’re all smart to know where to be on the ice and read off each other,” said Bergeron. “I think it will need a little bit of time, but not that much, because the game is going to be the best indicator of where we stand. So far I thought it was pretty good.”

“Loui is a different player. He’s a very good goal scorer and a great playmaker and he plays well in our end,” Marchand said about Eriksson. “I’m sure he’ll compliment us and we’ll play very well together.”

The one slight setback the second line could have: Bergeron’s injury. While he skated on Thursday, the Bruins assistant captain still hasn’t been cleared for game action.

At times during contact drills, the rib injury Bergeron suffered during the Stanley Cup Final was still a little sore. But for the most part, it wasn’t too concerning.

“It wasn’t bad. I felt it a couple of times in one or two battles, but it doesn’t seem to linger after it. It’s there for maybe 30 seconds or so and goes away,” said Bergeron, who’s entering his 10th year with the Black and Gold.

“I think I’m going to have to go through that for a couple of weeks and then I’m going to be fine. Medical staff isn’t too worried about it, so I’m not worried about it.”