Jose Mourinho's behaviour has rattled senior figures at Manchester United.
Mourinho was sent off during the draw with West Ham after kicking a water bottle.
"There's a fine line between madness and genius," a club source told the Daily Mail. "People react differently to pressure and he's obsessive about winning.
"Everyone thinks he can live up to his reputation as the Special One but the pressure he is putting himself under needs a release. After all, it's just kicking a water bottle.
"But there's no doubt it's 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."