UPDATE (3:58 p.m. ET): Matt Grzelcyk returned to the bench to begin the second period.
ORIGINAL STORY: The Bruins can ill-afford to lose any defensemen and may be down another one.
Grzelcyk, who had seven points in his last four games, immediately went down in pain on the ice. He remained there briefly before heading down the tunnel hunched over.
We will update this story as details become available.