Pogba captained the Red Devils to victory on the opening night of the new Premier League season, scoring the first goal of the campaign too, but suggested after the match that he was not entirely happy at the club.
The World Cup winner claimed that he was unable to speak his mind under Mourinho and suggested that things would be "easier" if there was more "trust".
The relationship between Pogba and Mourinho came under scrutiny on numerous occasions last season, while the France international's performances at this summer's World Cup led to claims that Mourinho could not get the best out of the midfielder.
However, The Telegraph reports that the Portuguese boss was left surprised by Pogba's comments as he had not voiced any complaints following his return to the club that week.
Mourinho is understood to be happy with his relationship with the 25-year-old and expects his players to raise any complaints with him in private, rather than to do so publicly.
The manager is expected to address the situation later this week in his pre-match press conference ahead of Sunday's Premier League clash with Brighton & Hove Albion.