Need 2 players per position. Tanganga is off and Dier can’t do high line. If Sanchez goes and we get Tosin then we will need another.
If Tosin is really good and 3rd choice then obviously we can bring in a 4th choice but all our defenders will clearly need to be suited to high line and also half decent on the ball.
I don't think four first team centre backs are particularly needed in a one competition season.
We can revisit in the January window if we're feeling a bit thin but if Romero, van de Ven and another can't be trusted over the next 4 months and the likes of Davies, Dier or one of the youngster actually have to be called upon within that time, I'd be surprised.