Don't think Barzagli will be used much next season. Caldera will probably stay at Atalanta for another season because we don't need him yet which makes sense why we should buy an experienced Benatia.
Bonucci, Chiellini, Rugani, Benatia, Barzagli...you won't find a club on earth with a more prepared, tough & experienced CB lineup. Caldera for the future probably with Rugani for Bonucci's final years. We are literally set for nearly the next decade.
If we can afford it, why the hell anyone would question the purhcase of Benatia is beyond me.