If rumors are to be believed, Spanish giant Real Madrid could leave English heavy weight Manchester United in a serious defensive dilemma, as the Santiago Bernabeu side is believed to be preparing a stunning £10-million summer acquisition of United's Serbian defender Nemanja Vidic.

With the United boss Sir Alex Ferguson already in deep trouble with his fragile defense that recently got battered by local rivals Manchester City at Old Trafford in a 6-1 mauling of United, Vidic's departure could be no less than a disaster. The manager has already sidelined Rio Ferdinand, who could leave the club and move on with the Spurs during the January transfer window.

Vidic is on top of Real Madrid boss Jose Mourinho's shopping list and his loss could prove to more problematic for United, according to a People.co.uk report.

Elsewhere, Spurs boss Harry Redknapp is currently tracking two of United's most experienced players - Rio Ferdinand and Michael Owen - and is keen to bag them during the January transfer window. Ferdinand has faced the heat since United's 6-1 loss against Man City and has been dropped from the first team.

Ferdinand's hope of featuring in United's first team is currently very bleak. To add to his woes, teammates Johnny Evans of Northern Ireland and Nemanja Vidic have been in good form. Young stars like Chris Smalling and Phil Jones have also impressed so far.

Vidic, 30, who joined United from Spartak Moscow in 2006 for a fee of around £7 million, has made 164 appearances for the Red Devils and has even managed to find the back of the net 14 times. He has also made 56 international appearances for Serbia.