Krug didn't finish the third period Tuesday against Carolina, and had an X-ray following the contest, Joe Haggerty of NBC Sports Boston reports.
At the moment it's unclear how Krug suffered his injury or the severity, and an update should be provided by the team in the upcoming days. Krug's been a steady presence on the Boston blue line appearing in each of the last 48 games, but if he doesn't recover for Thursday's tilt against Florida, Adam McQuaid figures to slot into his second-pairing role.