My theory is that no CB can be a Fernandinho-style-DM because CBs are most used to reacting to the game happening in front of them and can’t cope with the extra dimensions of being in the middle of the game. Same with FBs but at least they can generally add more pace/stamina than a CB is used to.
So according to this (my latest awesome enlightenment) we need to convert a CM or CAM to a DM. Just as Fernandinho I think was converted. Someone with a huge amount of energy, stamina, appropriate physical attributes, intelligence, can control the ball quickly and in very tight spaces, and has an exceptional passing ability.
Bernardo would fit the bill if he ate more greens as a kid.
Kevin DeBruyne is the man. I know he’s very good further up the pitch but the whole is greater than the sum of the parts.
(That’s my theory and I’m sticking to it for a day or two)