The report claims that United are willing to part ways with the Spanish international after singing Mkhitaryan for £26m from Borussia Dortmund.
United reportedly want to free up funds to bring in Juventus and France international Paul Pogba for a £100 million world record deal.
Mata was a £37.1 million club-record signing from when he joined United from Chelsea in January 2014. The Express claim that United are now willing to accept a cut-price £20 million offer for the Spanish intentional.
Mourinho also got rid of Mata when he was manager of Chelsea. Ironically the 28-year-old midfielder joined United and could now be destined for a similar fate under the same head coach.
Stoke City could face competition from fellow Premier League side Everton as well as Spanish outfit Villarreal.
Meanwhile Turkish giants Fenerbahce are in pursuit of a new attacking midfielder with Diego Ribas set to leave and have also been closely linked with Mata.