Collymore wrote in the People: "This summer simply has to signal the true end of the Sir Alex Ferguson era.
"So get ready for Manchester United: The End of Season Clearance sale. Everything must go! Well, almost.
"The old guard need to leave. The next generation must be ushered in.
"And the future should be built around Wayne Rooney and Adnan Januzaj.
"Those two players are as inspirational as they are irreplaceable and I don't believe you could say that about anyone else at the club.
"But when you look at the state of the squad, there is no doubt that a multi-million pound refurb is vital to turn them back into champions.
"You know what? I would even flog Robin van Persie if a big offer came in for him after the World Cup. Find a younger model for £20million, someone hungry to prove himself at the top level and become a club hero."