Defensively, we are having 5 at the back. To match with opponent’s attacking numbers. But in the build up phase, we build with a back 4. AMN pushing high or shifting inwards to join the other midfielders. Tierney would stay out wide as a left back, with Luiz and Holding as CB, and bellerin as RB. And this forms a back 4. Some other teams are a back 4 on paper but would have a CM dropped deep to CB position in build up. Wouldn’t that be considered as a back 5?