According to Ian Ladyman in the Daily Mail, the coach is "treading a fine line" with the Red Devils hierarchy, who believe he is hoping to pressure them into further spending despite him splashing out nearly £300 million on players since taking charge in the summer of 2016.
An unnamed but "prominent Old Trafford figurehead" has also privately expressed his belief that much of the speculation linking United with new players emanates from those around Mourinho.
Per Samuel Luckhurst of the Manchester Evening News, Mourinho recently said United are struggling to compete with Manchester City in terms of spending:
The Red Devils are 15 points behind the Sky Blues, who have also scored 19 more goals and shipped three fewer over 22 matches.
City have also splashed a great deal on players since Pep Guardiola took charge at the same time as Mourinho, having recruited the likes of Ederson, Leroy Sane, Bernardo Silva, Kyle Walker, John Stones and a number of others.
Sky Sports pundit Jamie Redknapp believes Guardiola would have been a better choice for United than Mourinho:
Similarly, Jason Burt of the Telegraph believes United are within their rights to want Mourinho to produce football similar to that of Guardiola's City:
The Special One has never been known to do so, though, and the Red Devils will have been well aware of his more pragmatic approach before taking the decision to bring him in.
That's not to say he can't produce exciting football at times, though—United started this season in superb form under him and scored four goals on six separate occasions in August and September.
The two managers' philosophical differences aside, Guardiola is getting much more out of his players than Mourinho, so there's plenty of room for improvement at Old Trafford without having to bring in more new faces.
Nevertheless, such is the gulf in class between the two, United could use some quality additions, and the club must ensure the manager can coax the best out of those that come in.