Nikishin was tracking a loose puck early in the second period when Kleven lined up and drilled the Russian D-man. He stayed down on the ice for some time, looking visibly dazed, before being helped off the ice.
In the immediate aftermath of the collision, Canes forward Andrei Svechnikov stepped in to defend his countryman Nikishin by pulling Kleven onto the ice and landing a flurry of punches.
Svechnikov was handed a double-minor for roughing, while Senators defenceman Jordan Spence was also handed a minor for roughing once the dust settled on the ensuing scuffles.
Tensions continued to boil over as both sides traded penalties through the second period. First, Sens’ centre Ridly Greig was called for interference after hooking netminder Frederik Anderson to the ground. Then, Carolina’s Nicolas Delauriers was given two minutes for unsportsmanlike conduct and two minutes for roughing, while Ottawa captain Brady Tkachuk was given a roughing minor for their roles in a scuffle between multiple players that broke out at centre-ice.
In between the chaos, Sens’ Dylan Cozens caught Jackson Blake with a cross-check behind the net, which sent the Canes forward off the ice.
The Senators entered the series down 3-0, on the brink of elimination.