The high-scoring forward was injured in the third period of the Devils' 2-1 victory over Florida on Saturday night. General manager Lou Lamoriello says he won't need surgery.
Lamoriello tells The Associated Press: "The team is the sum of its parts, and other players are going to get a chance to step up and contribute."
Kovalchuk was hurt when he slammed into the boards behind the Panthers' net. He briefly remained down before skating off and did not return.
Kovalchuk is second on the team with 10 goals and 27 points.
Heading into Sunday, the Devils were in seventh place in the Eastern Conference, in position to make the playoffs.