Manchester United star De Gea came close to joining Real Madrid back in 2015.
However, a faulty fax machine on deadline day ultimately saw him remain at Old Trafford.
The Spain international then signed a four-year contract extension with the Red Devils.
But, despite that, rumours of a move to Madrid have picked up again in recent weeks.
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Manchester United star David De Gea is wanted by Real Madrid
Ander Herrera wants David De Gea to stay at Manchester United
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Spanish outlet ABC claimed earlier this week he was desperate to finally move to the Bernabeu.
And Herrera has admitted that, though he wants his compatriot to stay, the prospect of De Gea leaving cannot be ruled out.
"I tried not to bring up the De Gea to Real Madrid topic," he told Spanish TV show El Chiringuito.
"It's difficult for him to one day be at one place, and then to be at another the next.
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"He learned a lot from this. It has made him more mature.
"I want him to be the one defending Manchester United's goal.
"Hopefully it will be like that, but anything can happen in football."
United have been linked with a move for AC Milan goalkeeper Gianluigi Donnarumma should De Gea quit the club this summer.