Diakite would be a decent option on a free.
You can see how Juve's defence suffers when it doesn't have the aggressive, dominating presence of Chiellini.
Not suggesting Diakite is anything close to Chiellini's level, but he could solve the issue of Juve's defence lacking muscle when Chiellini isn't there.
Despite being a big guy, he's still mobile enough that he shouldn't be too uncomfortable playing on the side of a back three.