Borussia Dortmund defender wanted by AC Milan
Rossoneri boss Massimiliano Allegri is unhappy that his side have conceded 19 goals in 15 league games this season and wants to increase his defensive options.
The 23-year-old German international has also been chased by Barcelona and Juventus in the past and would not come cheap given that his current contract still has five years left to run.
As well as a hefty transfer fee, they would be forced to pay the central defender a great deal in wages, something that is not currently in line with latest club policy.
The Diavolo are wary of the Financial Fair Play rules and hope to comply with them, as witnessed by the sales of stars such as Zlatan Ibrahimovic and Thiago Silva among many others during the summer.
Hummels has made over 100 appearances since joining Dortmund in 2009 and has made 23 appearances for the German national side to date.