Kaberle was taken off the ice on a stretcher after being blindsided by a late hit in the second period Friday night.
Kaberle was hit in the head by Janssen about 2 or 3 seconds after he made a pass in his own end of the ice. The Toronto player then fell to the ice and hit his head against the side boards at the Continental Airlines Arena.
Kaberle lay on the ice for a couple of minutes before he sat up. A neck brace was attached and then he was placed on a stretcher and wheeled off the ice.
A Maple Leafs spokesman said Kaberle was alert after being taken off the ice and that he was being taken to a hospital for observation.
Referees Kelly Sutherland and Brad Watson didn't call a penalty on the play.
Janssen will miss New Jersey's games against Boston, Philadelphia and Pittsburgh and could return at Buffalo on March 10. He will forfeit $7,220.16 because of the suspension without pay.
The Associated Press contributed to this report.