Manchester United legend Gary Neville is concerned over the departures of Nemanja Vidic and Rio Ferdinand.
It leaves United's new manager with Phil Jones, Jonny Evans and Chris Smalling as his options at centre-back, as well as untried youngsters Michael Keane and Tom Thorpe.
Neville told the Republik of Mancunia: "I think it's a big risk losing Vidic and Rio at the same time.
"There are young centre backs coming through, Phil Jones, Jonny Evans and Chris Smalling. And I think if we're signing a new centre-back coming from a different country who hasn't played here before, the idea of having a stalwart there would help.
"I think it's a risk. But we'll see how that pans out."
