Dier and Romero yes. Sanchez and royal are just a car crash waiting to happen. Get rid of them and find a van dyke kind of defender to push dier to keep his place. we have a real issue from set pieces
Sanchez was very good in place of Romero last season. His problem has always been positioning; as he often gets drawn out to the right. Playing in a back 3 seems to suit him better in this regard.
As a backup right footed CB, I am not convinced we could improve on Sanchez with a player that is happy to play 2nd fiddle to Romero.