The 53-year-old Portuguese is having to answer his third charge this campaign by the Football Association, for being dismissed for kicking over a water bottle in response to referee Jon Moss booking Paul Pogba during the 1-1 draw with West Ham on Sunday, since he arrived to much fanfare in the close season.
Mourinho, who has already been fined twice and served a one match touchline ban over the previous two charges, has not had the galvanising impact the board and the fans expected after he replaced the sacked Louis van Gaal.
The draw with the Hammers leaves them 11 points adrift of leaders Chelsea, who sacked him last season months after he delivered the title, and having made their worst start to a campaign since the 1989/90 season.
The United source told the Mail the pressure he placed on himself - quite apart from the pressure of expectations by others - and the way he was reacting to it had made several at the club ill at ease although the legendary Alex Ferguson was no stranger to emotional outbursts on the touchline in his heyday.
"There's a fine line between madness and genius," said the source.
"People react differently to pressure and he's obsessive about winning.
"Everyone thinks he cam live up to his reputation as the Special One but the pressure he is putting himself under needs a release.
"After all its just kicking a water bottle.
"But there's no doubt it has upset the applecart because he courts controversy in a way others haven't here.
"It upsets people at the club because they're not used to it."
Mourinho's next test will come on Wednesday when United host West Ham in an English Football League quarter-final.
Original source: Mourinho antics upsetting United hierachy