The England international has been frozen out at United after criticising manager Erik ten Hag on social media.
Sancho has been linked with a January return to Dortmund.
And Sky Deutschland says Dortmund coach Edin Terzic is in regular contact with Sancho.
A return is unlikely at the moment, but the idea cannot be ruled out as Terzic likes the player.
Sancho wants to leave United - which is open to releasing him on-loan in the New Year.