Look, what Mourinho is trying to do here is stick to a system and players, which is totally natural. He tried it last season and failed, and ended up defining our system almost always depending on the superior adversary, which was almost every team at a point, instead of imposing our way of play. I mean, we played the Europa League final with Fellaini as #10 (not criticizing it, just stating).
And actually, you just gave the perfect definition of reactive, “changing according to the opponent”, which is not what is looking for (again), if we except the Real Madrid Super Cup. Let's see if now, after our next setback, he gets more careful or not. That's when a player like A.Pereira might come handy.