United face the Real Madrid superstar on Wednesday in their Champions League clash at Santiago Bernabeu, four years after flogging him for 80 million pound, the Sun reports.
Ferguson said if any club wants to buy back Ronaldo then they must be ready to shell out hundred of millions, adding that rules everyone out, including Barcelona.
Ronaldo who moved to the Bernabeu in 2009, has been heavily linked with a switch back to Old Trafford.
But boss Ferguson said everyone talks about it but he doesn't see it, adding Ronaldo has two and a half years left on his contract and Madrid is trying hard to get him a new contract. (ANI )