Tkachuk was assessed a five-minute major for spearing and a game misconduct after striking the back of Luke Witkowski's leg with his stick, thereby inciting further fisticuffs.
This, according to the league, constitutes unsportsmanlike conduct on Tkachuk's part.
Witkowski was heading to the locker room at the time, as a result of a game misconduct of his own, and has since received a 10-game suspension in accordance with NHL Rule 70.6.
This marks the second suspension of Tkachuk's young career after he sat two games in 2016 for elbowing Los Angeles' Drew Doughty. His repeat offender status was taken into account in the decision.