I don't know what you could tell your defenseman in that situation? Guy is coming into the zone, with the puck, head down. Trouba didn't raise his elbow to hit the guy, didn't jump, just made a good physical hockey hit. Its a good thing Trouba isn't shorter or he could have done a lot more damage with his shoulder to the players head.
I guess that is contact to the head, but you're telling me that from now on you can't hit a player with his head down?