The 29-year-old, who has kept 176 clean sheets in 352 appearances for the club since arriving from Benfica in 2014 and is rated as one of Europe’s top performers in goal.
Oblak signed a new contract this summer that ties him down to the club until 2028. But United will be hoping to pay a fee that is considerably lower, particularly if the Slovenia international makes clear his desire to move to Old Trafford.
The club have been keeping tabs on his situation with Atletico also eyeing a new long-term goalkeeper, having been linked with Greek international Odysseas Vlachodimos who plays for Benfica.
Alternatively, United signing Oblak could leave the door open for De Gea to return to his boyhood club should Los Rojiblancos decide to move for the former Atletico trainee.