Ronaldo moved to Real Madrid in 2009 and subsequently established himself as one of the greatest players of the age, if not of all time.
The forward spent 95 million Euros to sign the Portugal international, but now 30, and with relations frayed with Real chief Florentino Perez, it remains to be seen whether the ex-Sporting Lisbon man will still be at the Bernabeu for much longer.
United have the resources to bring their erstwhile hero back to the club and, with Angel Di Maria heavily linked with a move away from Old Trafford to Paris Saint-Germain, the Red Devils may imminently have a need for another explosive, offensive wideman.
According to Le 10 Sport, the Red Devils are keeping an eye on their former star and Ronaldo, who loves United, is keeping the door open to a return to Manchester.
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