Krstović arrived at Atalanta from Lecce last summer for around 25 million euros, and this season he has established himself as an important part of Rafaele Paladino's team.
He has scored nine goals in the championship so far, so his market value has increased and is now, according to Italian media, estimated at around 35 million euros.
Milan have already brought in Andrej Kostić. If Krstović were to arrive at San Siro, the Rossoneri would have an interesting Montenegrin attacking duo.