Pittsburgh head coach Dan Bylsma said the Penguins star will not play against the New York Islanders in Sunday night's home game.
The reigning NHL MVP had just returned to the lineup after missing four games with a concussion last month.
The Penguins centreman suffered the injury after taking a strong hit from Maple Leafs winger James van Riemsdyk in the third period of Pittsburgh's 5-4 shootout win over Toronto on Saturday. Malkin played one more shift before leaving the game.
Bylsma said Malkin was kept off the ice for precautionary reasons, adding that he will be re-evaluated.
Malkin has tallied five goals and 19 assists in 21 games this season for Pittsburgh.