I don't really know Barbosa, but isn't he super hyped? Imagine he would go for a lot more than 20 million €...
Anyway, if we should believe reports, Pjaca and Benatia seems to be on their way.
That would give us a squad like:
Buffon, Neto, Audero
Lichtsteiner, Alves, Cheillini, Bonucci, Barzagli, Rugani, Benatia, Alex Sandro, Evra
Marchisio, Pogba, Khedira, Pjanic, Asamoah, Lemina, Sturaro
Dybala, Mandzukic, Zaza, Pjaca
Assuming Pereyra and Hernanes are on their way out. That's 23 players, with Audero and Marchisio as home grown. Means someone would have to go if we were to aquire another player, unless he is under 21. Pretty competitive squad, though we could be a bit short in the strikers department.