Evgeni Malkin just returned this past week after missing four games with a concussion.
Late in the third period of the Penguins' 5-4 shootout win over the Toronto Maple Leafs he was on the receiving end of a big hit along the boards from James van Riemsdyk.
He skated off on his own, and was able to return for one brief shift, but did not play over the final seven minutes of regulation or the overtime period.
The Penguins said after the game that it's an "upper body injury" and not a head injury, and that he was kept out of the lineup for precautionary reasons.
Pittsburgh returns home on Sunday night to play the New York Islanders.