Demiral has three years more remaining on his contract with Juventus, but could be allowed to leave the Italian top flight club this summer.
The 23-year-old has attracted interest from the Premier League, with Everton and Tottenham said to have put in enquiries for the central defender.
As Demiral attracts transfer interest from England, Juventus are prepared to part ways with him and are already planning for life without the Turkey international.
According to Italian daily Gazzetta dello Sport, the Turin-based club have identified Fiorentina defender Milenkovic as an ideal candidate to replace Demiral.
Newly-appointed Juventus boss Massimiliano Allegri is keen to have four top centre-backs at his disposal and wants to replace Demiral with Milenkovic, should the Turk leave the club this summer.
Milenkovic, though, has also been linked with a move to the Premier League, where Everton, Tottenham and West Ham have been credited with an interest in him.
Though Everton and Tottenham have been linked with several players, the Premier League duo are currently without a manager and may only step up their interest in transfer targets after they have appointed one.