The Bergamo club, who are having another fine season under Gian Piero Gasperini, risk losing Castagne this summer.
The Belgium international is out of contract in June 2021 and has shown no signs of renewing his contract.
The likes of Inter, Napoli, PSG, Tottenham, Leicester and Sevilla have been linked with Castagne.
And if he does leave, Atalanta will move for Lille’s Turkish international Zeki Celik.
23-year-old Celik has appeared 32 times for Lille this season, including in all six of their Champions League fixtures.
Celik, who is familiar with the three-at-the-back system, would cost Atalanta around €15m.