According to The Sun, the Italian giants are keeping tabs on the 29-year-old as speculation grows surrounding his future at Old Trafford.
Onana joined Man United from Inter back in the summer of 2023 but has failed to convince between the sticks at Old Trafford.
Amorim decided not to start the Cameroon international in their Premier League opener against Arsenal on Sunday, instead choosing to play Altay Bayindir.
The manager told Sky Sports before the game: "It's an option. We try to choose the best players for each game. Next week is a different life and in this week we chose this way."
Pressed further on Onana's absence, he added: "No, no (not an injury). He (Onana) will recover but the guys did so well in pre-season so I need to balance that."