We have hardly seen anything of Fernandes just yet, yet, I doubt we will buying him from Lille, his contract there runs till 2028. We need to find someone who is willing to buy Pröpper, since we paid 3m for him last summer.
I don't think he is that bad a defender, but we either revolve our centre-halfs like there is no tomorrow, or hardly ever. How shall Pröpper, Fernandes, Nsiala, Sterling et al create a settled defensive partnership with Souttar or Balogun, if they are constantly shifted in and out. Probably also a problem of not having a B team to create a partnership 1, 2, and 3, who can come in as a "block". Similar to changing "blocks" in ice-hockey, i.e. defensive lines and attack lines. People know one another and can cope with situations. More often than not, we throw on make-shift combinations and end up with headless moments time and again, if these chaps come under pressure.
Having watched how people play, you wonder whether we can adopt this three at the back, but with someone like Sterling (if fit, but he played well there before) or Nsiala in front of them. That area is seriously lacking bodily strength and, Diomande apart, the vision to spot danger quickly enough AND react appropriately (like Lundstram, Davis, and Jack did in the past). Nsiala has the strength and pace to do this.
IMHO, our current best CH partnership is Balogun and Souttar. Neither are world beaters, but they click and compliment one another better than the rest. Put someone decent (see above) in front of them as extra cover, and we could breathe a little easier in most games.