Following failure to get the deal over the line in time, the blame game has commenced, with neither club wanting to take responsibility.
But the Madrid president has blamed the Red Devils saying they took over eight hours to send through the contracts.
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The 68-year-old claims the Old Trafford club received the paperwork at 1.30pm, but took a ridiculous amount of time to return the files.
Perez then made a thinly veiled insult towards the Manchester club and Ed Woodward, claiming they lack experience at getting deals done.
Of course this is not the first time Madrid and United have failed to get a deal over the line, with Fabio Coentrao's loan move falling at the final hurdle in 2013.
Perez made his comments while talking to Spanish radio station Cadena Ser, said: "I think what they lack is experience, it happened last year with [Fabio] Coentrao, exactly the same. They have a new team and they lack experience
"We have worked with them before [without problems], with Peter Kenyon and David Gill and with Sir Alex Ferguson. We still have good relationship with Manchester United but this is the exactly the same as happened before with Coentrao and Herrera and we thought they would have learned from what happened in the past.
“At 13.30 Manchester United had all the papers but they took eight hours to return them, we couldn’t buy him before because Manchester United didn’t want to sell him."
A lot has been said about what the future holds for Manchester United and David de Gea. Will he play? Will he sign a new deal? Will he leave on a free? But whatever does happen, the Spaniard must return to the starting line-up.
He is head and shoulders above Sergio Romero, who has deputised in the 24-year-old's absence, and could be pivotal in helping United challenge for the title this season.
For the goalkeeper himself, Spain coach Vicente del Bosque has already warned him over his chances for the national team if he is not playing, so he must get on with it.
Whether he signs a new deal is still up in the air, but it would take something pretty incredible for the want-away keeper to put to pen to paper.