Eichel last played Sunday against the New York Islanders, suffering the injury after being checked by Casey Cizikas.
"An injury of this nature just needs more assessment and more time to understand it. I'm being honest with you: We do not know for certain the time frame," Krueger said of Eichel's injury.
Dylan Cozens is also out against the Penguins on Saturday as the rookie is listed as day-to-day after an injury sustained from a hit by Pittsburgh's Zach Aston-Reese on Thursday night.
Cozens has three goals and two assists in 20 games played.
Eichel, who was in the midst of a 13-game scoring drought with just two goals this season, had netted an assist in each of his last four games played before suffering the injury.