London, Nov. 1 (ANI): Manchaster United boss Sir Alex Ferguson is set to buy back Ryan Shawcross, as defender Rio Ferdinand is struggling with his form due to persisting back injury.Shawcross, 21, left Old Trafford at the start of 2008 for a one-million-pound deal.But even after his departure Ferguson kept an eye on his progress, and nearly re-signed the Stroke defender during the summer.

Now, it is up to Ferguson whether he would move for Shawcross in the January window or wait until the end of the season.

According to News of the World, the continuing stuttering performances of Ferdinand and Nemanja Vidic could prompt Ferguson to act sooner than later.

Shawcross would be eligible to feature in the Champions League knockout stages.

When Ferguson sold Shawcross, he insisted on a clause that means Stoke must give United first option on the player.

A host of big clubs, including Liverpool, have shown a major interest in Shawcross.

Should one of those clubs make a bid that Stoke find too hard to resist, United must be given the chance to match it.

Otherwise, Ferguson will have to make his own bid, which is expected to be around eight million pounds. (ANI)