The injury happened with 4:03 left in the first period on what appeared to be a harmless-looking play.
Leafs centre Leo Komarov raced wide and fired a wrist shot that appeared to hit Luongo on the top of his right shoulder and then the side of his head.
The Panthers goalie Luongo immediately went down to the ice. After a lengthy visit from the team trainer, Luongo remained in the game and finished out the first period.
However, he was replaced in the second by backup Al Montoya.