Atletico are unable to sign anyone until January after a FIFA-imposed transfer ban was upheld last week.
The news provoked Antoine Griezmann to commit his future to the Spanish club amid serious interest from the Red Devils.
He said it would be "a really harsh blow" to leave Atletico in their current situation.
But Oblak, 24, is apparently not of the same mind.
The Manchester Evening News claim the Slovenian goalkeeper would still be open to a move away from the Spanish capital.
And that could come as a boost to Jose Mourinho, who is said to be eyeing a move for Oblak in case David De Gea joins Real Madrid this summer.
Chelsea and Real are also interested according to the Manchester Evening News while French giants Paris St-Germain are specifically said to be "pushing a lot" to do a deal.
Oblak was named Spain's best goalkeeper for a second season in a row after another impressive campaign.
He made 41 appearances in all competitions, keeping 21 clean-sheets in the process.
But the stopper won't come cheap, with his current Atletico deal said to include a mammoth £85m release clause.
Oblak's agent last month confirmed Premier League interest in his client.
He said: ”Above all, there are two clubs that are really interested in Oblak for next season.
"One is certainly from the United Kingdom."
