Would you prefer a flashy signing? Or let's say a Zaniolo and Pellegrini? Adding a Tonali or Aouar would probably be too much on top of that but maybe not?
Pjanic and Rabiot out leaves space for two. I see Pogba, Aouar, Zaniolo, Pellegrini and Tonali as all playing in a mezzala role with Sarri, so you will probably only see one of these players join. Cost probably also dictates that, Pellegrini aside. If Khedira were somehow to be convinced to release his vice-like grip then you could bring in two. If Pjanic leaves then realistically you need someone to play DLP, as Bentancur can play there but is a little wasted, and there is no reserve.
It seems likely that we will see at least 4, and as many as 7 player changes in the next window. Maybe now is time for the midfield overhaul. We started it with Kulusevski and look to be pressing with more.
As an example:
OUT
Rabiot
Pjanic
Bernardeschi
Khedira
IN
Jorginho
Pogba
Mandragora
Bentancur - Jorginho - Pogba
(Kulusevski) (Mandragora) (Ramsey) (Matuidi)
That's 7 players for three spots, but also 3 of those players can be used as wide attackers or as an AM, so it gives options.
I wouldn't get rid of DC, nor do I think it will happen in the next window. If you get rid of DC then you have to look at someone like Chiesa. I don't think Boga plays RW at all.
For right back, I believe Danilo and Cuadrado will rotate again, plus Demiral can play there as a defensive right back. It wouldn't surprise me if we don't sign a right back. We'll probably make a future right back signing next season, to be used the season after next. At that point Cuadrado will be 34 and probably lost most of his speed.
Pellegrini coming in to replace MDS makes most sense, but we've seen before we go light in those areas, and may even stick with Alex Sandro and Danilo as left back options only (with Matuidi an emergency).
Idea as a depth chart:
GK) Szczesny, Buffon, Pinsoglio (3)
DR) Danilo, Cuadrado, Demiral (3)
DC) De Ligt, Chiellini, Bonucci, Demiral, Rugani/Kumbulla (5)
DL) Alex Sandro, Danilo, [Pellegrini] (2/3)
RCM) Bentancur, Kulusevski, Ramsey (3)
DM) Jorginho, Mandragora, Bentancur (3)
LCM) Pogba, Matuidi, Ramsey, Mandragora (4)
AM) Ramsey, Pogba, Kulusevski, Dybala (4)
RW) Dybala, Douglas Costa, Kulusevski, Cuadrado (4)
LW) Ronaldo, Douglas Costa, Ramsey (3)
CF) Higuain, Ronaldo, Dybala (3)
Personally I don't see us signing Pogba at all, so you could swap him with one of the other options.
