Wow, is that really it?
I missed that in the game, but from the reaction some people have had to it I thought he fully clothes lined Naholo.
Unfortunate accident, there's nothing in that at all.
I agree it is not as bad as some were describing, however it was a swinging arm with force to the neck so should have been a penalty and yellow. I think the difficulty people have at the moment is with unintentional/accidents. I don't think O'Brien had any intention, but players now have a duty of care and he swung his arm into Naholo towards the neck/shoulder area. Again like I said for SBW, don't give the ref/citing blokes the opportunity to interpret it.