Krug (undisclosed) did not return to Saturday's Game 2 after leaving in the second period following a hard hit by Toronto's Jake Muzzin.
Krug had tried to stand, but he looked more like Bambi on ice than an NHL defender. He had only played in five games at the end of the season following his last concussion. Krug is a valuable part of the Boston blue line; his loss will be significant. Hopefully there is an update on his health Sunday.