The 19-year-old forward hit Doughty in the face with his left elbow during the Flames' game against the Kings on Sunday. Despite Tkachuk having no disciplinary history, the league ruled the elbow to be reckless and forceful enough to warrant a suspension.
Tkachuk, son of former NHL forward Keith Tkachuk, will forfeit $10,278 in salary. The No. 5 pick in the 2016 draft has 13 goals and 33 assists for 46 points in 68 games in his rookie season.
"While we are disappointed with the League's verdict, we nonetheless respect the process and that the League has issued its ruling," the Flames said in a statement. "Both the Flames and Matthew accept the decision. Our sole focus now is on preparing for our game tonight in Washington, while Matthew will spend the next few days getting ready to return to the line-up on Saturday in St. Louis."
Information from The Associated Press was used in this report.