Eriksson was injured at the 5:49 mark of the third period against the Sabres, taking a blindside hit to the head from Buffalo enforcer John Scott after dumping the puck into the offensive zone. Scott was issued a charging match penalty.
Eriksson did not return to the game and was held overnight in Buffalo as a precaution.
"Loui traveled back to Boston from Buffalo by plane [Thursday] with a member of the Bruins medical staff," Chiarelli said in a statement. "After an examination by team doctors in Boston, he has been diagnosed with a concussion and will be out indefinitely. The team will provide a further update on Loui's status when appropriate."
Scott was suspended Thursday pending a disciplinary hearing for the hit.
Scott has been given the opportunity to attend an in-person hearing, which has not yet been scheduled. The hearing is offered when a suspension has the potential to exceed five games.
"I didn't like the hit, didn't like it at all, didn't think it was necessary obviously," Bruins president Cam Neely said on 98.5 The Sports Hub on Thursday. "I'm sure the league will look long and hard at this, because ... the start of the season, what's happened so far, is something that none of us want to see happen. There's got to be way to try and figure this out. There really has to be, because we're losing good players to concussions."
Scott defended his style of play and said he didn't intend to injure Eriksson.
"I don't think I'm a dirty player. I try to play within the code and within the rules," he said after the team's practice Thursday. "This is my first suspension, and I don't think I'm a dirty player. I don't try to be a dirty player. I feel really upset. I was sick to my stomach last night knowing what happened and watching the video; I just kind of regret the situation. I don't want to be a dirty player."
Scott said he texted Eriksson to apologize.
Information from The Associated Press was used in this report.