Hagens (lower back) was injured in the third period of Thursday's game versus the Penguins and didn't return, Scott McLaughlin of WEEI reports.
Hagens was checked in the back by Samuel Girard in the third period and came out of the interaction worse for wear. The Bruins are off for a couple of days before hosting the Panthers on Sunday, which may give Hagens enough time to recover. If he and Matthew Poitras (nose) are both out, the Bruins may need to recall a forward from AHL Providence.