With delays continuing over new contract talks between United and De Gea, it is only fueling speculation that Perez can bring the former Atletico keeper back to Madrid this summer.
Diario Gol says Mourinho is prepared to sell De Gea - but only if the right player is included in Real's proposal.
Perez's offer of Gareth Bale hasn't been rejected completely by Mourinho, but for the moment he is insisting on other players knowing he holds the upper hand in negotiations.
The two Real stars Mourinho has demanded are Toni Kroos and Marco Asensio. However for Perez, neither player can be considered for sale - for now.
De Gea's popstar girlfriend Edurne, meanwhile, has been house-hunting in Madrid this year in anticipation of his return.