United signed Sanchez from Arsenal back in January, landing the 29-year-old in a straight swap with Henrikh Mkhitaryan.
The attacker was an expensive addition last January, as Sanchez and his agent demanded huge signing-on fees as well as a weekly wage of £500,000.
Sanchez has failed to replicate his Arsenal form in United and the Daily Star claims United are exploring the possibility of selling the 29-year-old in January.
It is understood Mourinho is planning to axe Sanchez permanently from his squad, despite the head coach denying his team were light in attacking options without him.
So far, however, Sanchez Manchester United career is yet to lift-off. The Chile international has managed just three goals from 23 outings for the club so far.
However, other publications have claimed that, should Zinedine Zidane succeed Jose Mourinho as manager, Sanchez may be sold.
And Coral have PSG and Arsenal as frontrunners for his signature.
The Ligue 1 giants were linked with Sanchez in January as his career in north London dwindled down.