Kaberle, who was conscious and communicative after being taken off the ice on a stretcher, spent the night under observation in hospital.
No penalty was assessed on the play by referees Kelly Sutherland and Brad Watson.
Colin Campbell, the NHL's discipline czar in his role as head of operations, spoke with Janssen by telephone before announcing the suspension. Campbell indicated he felt the hit was late.
Kaberle was hit in his own end after passing the puck to Carlo Colaiacovo. The puck was on Colaiacovo's stick when Janssen drilled him in the head with his left shoulder. Kaberle spun head-first into the side boards and appeared to be unconscious as he lay face down on the ice. He was sitting up on the ice when a plastic brace was attached to his neck before he was strapped to the stretcher.