We need two Fullbacks on both wings - one top notch and one very good (or youth talent) to rotate (say 60%/40%) as the modern fullback has to put in a real shift and simply has to be rotated with another to keep up the required level of skill and fitness. Pep's need for them to help out in central defensive midfield means they will burn out otherwise.
I've seen enough to know Maffeo can be at least our 2nd right fullback. The question is who will be the other 1?
Fabinho (from Monaco) is absolute quality and I'd be happy to see him on our right - Indeed I was extremely disappointed we didn't do the deal last summer. Hector Bellerín would be my other choice as the number 1 right fullback - he is proven quality and currently just about Arsenal's best player.
City do also seem interested in Celtic Soares at Southampton to be right back but this is probably an option instead of Maffeo - which would be a shame as Maffeo was tremendous against Utd in the League Cup but for some reason never got another chance!
Left back is a big issue for every club in the world right now. The best are past their peak and there really are not any truly outstanding up and coming talents except one (more later).
Danny Rose from Spurs good option as a left back as he is great going forward though there is a slight question mark over his defending - indeed he has made a number of mistakes in high profile Spurs games. Also, he will be incredibly expensive as Spurs will milk us dry to buy him. Perhaps a cheeky bid for Luke Shaw would do the job? he certainly has the talent - but does he have the desire?
My main choice, however, would be 20 year old Lucas Hernandez from Atletico Madrid. He can play left back and centre half and would be the ideal player for Pep to swap formations between 4 and 3 at the back. I'd actually totally break the bank to get this lad as he is clearly world class and will be one if the best in the world for years to come.
Then again all I know is so long as it's not Clichy (good service but struggling for pace now) or Kolarov (except in a dire emergency) I don't really mind.