I reckon the team needs 7 senior mids + Mandragora. This is because in the end I see the squad with 2 senior keepers, 9 senior defenders, 4 senior forwards (+maybe an U-21 Barbosa). Assuming Marchisio is the only senior HG player we would be allowed only 22 senior players.
Assuming Pogba goes, this would be the list:
1 Khedira
2 Marchisio
3 Pjanic
4 Hernanes
5 Sturaro
6 Lemina
7 Asamoah
8 Pereyra
+ Mandragora
So, if we bring another mid in then 2 of the above players need to go. At this stage it should in theory be Pereyra and Hernanes. So my guess is, we may not sign this so called Pogba replacement until we have finalized the exit of those 2 players.