Last night, Derek MacKenzie had a big hit against Phoenix's Oliver Ekman-Larsson. The play didn't draw a penalty at the time beyond Keith Yandle challenging D-Mac to a fight, but it appears that the NHL's department of player safety felt otherwise.
MacKenzie will have an in person hearing this afternoon, which means the NHL could suspend him for more than five games. He has never faced supplemental discipline before, which helps, but the hit did take OEL out of the game, which seems to fit the trend of suspending to the injury, not to the actual play.
After watching the hit a few times, I would say it probably deserved a boarding call, but I don't see an intent to injure. MacKenzie gives him a pretty solid blow, and Ekman-Larsson does go hard into the boards as a result, but the impact was pretty much a center mass hit, not a headshot or deliberate attempt to put him into the turnbuckle all Shea Weber style.
I will say that MacKenzie does give an extra shove as he delivers the check that probably isn't necessary, but this doesn't feel like a five+ game suspension to me. I could see two games, just in the sense of "don't do that again", but we've seen far worse incidents go unpunished in the past.
If Ekman-Larsson had stayed in the game, would this have come up? Honestly, I feel like the answer is probably not. This looks a like a case of the NHL deciding to take action because the player left the game, not for the severity of the incident, but we won't know for sure until we learn the outcome of the hearing.