Tackling from behind and not playing the ball first is at least a Yellow card not a simple foul.
I may be blind but I do not see Mastroeni playing the ball either. In addition, I see many cleats.
That said, most refs would have given him a Yellow, not a Red. It didn’t seem to be violent enough to be a Red card. There did not appear to be the intent to cause harm to the Italian.
I think that the ref should be commended for seeing and calling De Rosse’s cheap shot against McBride. Most refs would not have seen the hit so clearly. Excellent positioning.