Milan were said to be initially interested in Sassuolo's Stefano Sensi but his higher price tag has shifted their focus to €20 million-rated Duncan.
With the seven-time European champions already boasting of similar midfield options in Kessie and Chelsea loanee Tiemoue Bakayoko, there have been concerns about where the Ghanaian could fit in the set-up of Gennaro Gattuso.
Latest reports, however, say Tottenham are upping their interest in Kessie, a situation that could make more room in the midfield of Milan, who are looking to swoop for Duncan should they lose the Ivorian.
The Black Star is currently enjoying a fine season in Serie A, having notched three goals so far - two strikes better than his previous record.
He has made 12 appearances in the topflight this term - all starts - and also has two assists to his name.
He was once on the books of Inter, Livorno, and Sampdoria.