When they came out with the major for contact to the head, my cinical first response was to have everyone skate with their head down because no one could hit them.
If Trouba had just been standing in the guys way and braced for the hit the opponent, by lower his head, would have run his head into Trouba's elbow and gotten blown up because he had no idea what was in front of him.
I think it was a clean hit. He certainly didn't lead with his elbow out. Contact to the head certainly, but whose fault was that? I put it more on the guy skating with his head down.