After blocking a shot in the second period, Johnsson fell to the ice in pain. He returned briefly, but did not return for the third period.
After the game, head coach Mike Babcock said X-rays came back negative but the 24-year-old will miss practice on Sunday. The Leafs play their next game Monday against the Columbus Blue Jackets.
For now, with John Tavares out for the foreseeable future with a broken finger, the Maple Leafs are without two of the top-six forwards from their opening night roster.