The Nerazzurri have taken just one point from their opening two fixtures.
“We know we have a strong team and we can do very well," De Vrij told Sky Italia.
“But we also know we have to do more than what we've done in the last two games.
“A three or four-man defence? It's all the same to me, last year I always played in a back-three so I got used to that formation."