Directly following a faceoff against Erik Haula, MacKinnon took a whack at the referee who had dropped the puck, and the play did not look accidental in the least. Have a look for yourself below.
After the league making an example out of Brad Marchand for taking liberties on Pittsburgh Penguins netminder Tristan Jarry, I have a hard time believing that the NHL issue MacKinnon a suspension any less than the 6 games that they gave to Marchand. Granted, Marchand has a lengthy history, but even he isn't hacking an official in the leg.
This was a bonehead mistake by MacKinnon and I could easily see a 10-game or even a 20-game suspension occurring here. If the league views it as "Abuse of an Official", I believe it carries an automatic 20-game suspension. There are subsections of the rule that allow for lesser suspensions, so it will be interesting to see which way the NHL goes with this one.