The left-back position has been a problem for Jose Mourinho since he took charge of the club last year.
United spent £27million taking Luke Shaw from Southampton but he has struggled to convince Mourinho he is worthy of a starting spot.
It now looks highly likely that the England international will leave Old Trafford when the transfer window reopens.
Mourinho has converted Ashley Young into a makeshift wing-back so far this season to good effect, but it is thought he is wanting to strengthen the position to try and keep tabs on league-leaders Manchester City.
The Daily Record report that United will give Mourinho an £80m transfer kitty next month.
And Sandro’s desire to leave Juventus in the new year has perked ears in Manchester.
The Italian champions’ head coach Massimiliano Allegri has already stated that his full-back will not be sold mid-season unless they receive a “crazy offer”.
Chelsea have been monitoring the Brazilian closely and it has been reported this week that they are edging closer to a deal.
The Brazil international has been on Chelsea's radar since the summer.
But United will be hoping to turn Sandro’s head.
However, they will have to dig out a world record fee for a defender if they are to capture his signature.
Juve are apparently holding out for a figure around £61m.