The pair were regulars for the Premier League side this past season.
The pair were first-team regulars under Louis van Gaal, but Sky Sports is claiming that should an acceptable bid come in for either of the pair, then the Dutchman's successor will not stand in their way.
Mourinho was in charge of Chelsea when Mata completed his move from the Blues to Old Trafford in 2014, and Sky Sports claims that the frustrations he had about the Spaniard's game that led to the switch still exist.
Meanwhile, Sky Sports adds that Blind will be allowed to move on after just two years with the Red Devils as he does not fit the blueprint for the kind of centre-back that Mourinho likes to work with.
While neither player has been able to inspire the team back to the heights that they scaled under Sir Alex Ferguson - though Mata scored the equaliser in their recent FA Cup triumph - they have both been key men this past season.
No player in United's squad has made more appearances in the Premier League than the pair, while only Anthony Martial and Wayne Rooney scored more goals than Mata, and only the captain contributed more assists than the playmaker.
And with Blind helping the side keep the joint-strongest defensive record in the division, it is perhaps a surprise that they could both be heading for the exit, though Mourinho may feel that a fresh look to the squad is required to end their wait for the title.