Teammates and referees had to pick Ottawa rookie center David Dziurzynski off the ice after Maple Leaf Frazer McLaren knocked him out 26 seconds into the game.
McLaren fired off a few quick jabs after a face-off in the Toronto zone, and Dziurzynski went down.
Dziurzynski reportedly has a concussion, and is listed as day-to-day.
It was the sixth fighting major for Ottawa this season, but the league-leading 24th for the Maple Leafs, despite going three straight games without a tussle. McClaren has already equaled all of Ottawa with six fighting majors this year.
The Toronto Sun points out the Maple Leafs may be trying to make a statement to the rest of the league.
Bitter rivals, now third in the Northeast, Toronto holds a two-point advantage over the Senators.
The video below shows the fight in its entirety.