The necessary paperwork for the transfer was not submitted before the cut-off point of 11pm in Spain. Pending an appeal it seems likely De Gea will remain at Old Trafford until at least January.
But failure to get the Spaniard's deal complete does not mean Keylor Navas' proposed move to Man United is off the table.
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The Costa Rican stopper was set to be used as a make weight in the deal for Spain's current number one, and was in line to see his wage doubled from €2 million to €4m if the deal went through.
And the Mirror, via Spanish newspaper El Confidencial, are reporting a deal involving Navas could still go ahead after a €15m deal for the goalkeeper was completed and personal terms were agreed.
The Red Devils still have until 6pm today to complete any deals, but special dispensation to complete deals after the deadline is given in the UK, unlike Spain.
With De Gea's deal falling through it would seem unlikely Madrid would allow Navas to depart the Bernabeu. But with Los Blancos so keen to swap the two goalkeepers, the 28-year-old may feel his future lies at Old Trafford regardless.
There is a slight possibility De Gea's move could still go through if Madrid decide to appeal, however the decision would lie solely will FIFA.
With Victor Valdes seemingly likely to stay put at United after changing his Facebook header image, the Red Devils could have an embarrassment of riches in the goalkeeping position.
However nothing is clear in the transfer window and everyone is patiently waiting to see which goalkeeper ends up where within the next 24 hours.
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