Former Manchester United defender Phil Neville has called on the Red Devils to do all that they can to keep hold of goalkeeper David de Gea.
The Spaniard has been strongly linked with a move away from Old Trafford this summer, with European champions Real Madrid understood to see him as a natural successor to Iker Casillas.
The 24-year-old's current contract expires at the end of next season and, with talks over an extension still ongoing, Neville fears that the stopper could depart.
Neville told BBC Sport: "It is imperative David de Gea stays at Manchester United.
"He is the one player in the summer they have to sign. I have never seen a player develop so quickly as David de Gea has at Manchester United."
De Gea was named in the PFA Team of the Year last month, having helped United to the brink of a Champions League return this season.
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