Manchester Untied will turn their attention to Joe Hart, Samir Handanovic or Gianluigi Donnarumma, if goalkeeper David De Gea leaves for Real Madrid.
According to The Sun, United are confident of holding onto De Gea, but they have constructed a list in case circumstances change.
Hart is unwanted at rivals Manchester City, further highlighted by the signing of Benfica keeper Ederson.
AC Milan wonder kid Donnarumma is stalling on signing a new contract with the club, with his current deal due to end next season.
Inter Milan are believed to be open to selling their stalwart Handanovic, who has a contract at the San Siro until 2019.