The furious Portuguese boss left the volatile teenager at home in Italy as part of his no-nonsense preparations ahead of Tuesday night's make or break showdown at Stamford Bridge.
Balotelli, 19, was mysteriously omitted from the Inter squad, named by Mourinho yesterday, and the player's agent Mino Raiola insisted yesterday he had no idea why he had been omitted.
An Inter source told Goal.com: “Balotelli wasn’t called because he had a massive argument with Mourinho. They are having a personal feud and even though Mourinho thinks he is talented, he has made it clear that he will not tolerate his terrible attitude.
“Mourinho had enough of his behaviour and couldn’t risk jeopardizing the most important game of [Inter’s] season.”
Balotelli’s omission from the squad is in keeping with the 'Special One's' ultra-serious attitude to his team's preparations.
Inter are the only remaining Italian team in the Champions League and hold a narrow 2-1 lead after the first leg at San Siro a fortnight ago.
The usually jovial Mourinho sat stony faced in his pre-match press conference yesterday evening, and didn’t interact with the media too much.
When specifically asked why Balotelli had not been summoned, Mourinho sternly replied: “Balotelli? I'll only talk about who is here.”
Inter president Massimo Moratti admitted his surprise when learning of Balotelli’s exclusion, while the teenager’s agent Mino Raiola says that his client was “bitter, sad and disappointed” by Mourinho’s decision.
Goal.com can also reveal that Inter have brought over a formidable entourage of players and other staff – including directors and medical personnel – to London.
The club booked out the City's trendy Italian restaurant L’Anima on Monday night, and more than 50 Inter staff members dined at the Italian eatery which has been tipped to win a Michelin star.
Amongst the group, who enjoyed a specially-created £80-a-head menu, including traditional southern Italian dishes such as Stracciatella Tortelli and Wild Sea Bass with Smoked Aubergines, was Mourinho's wife Tami and his son Jose Jr.
The Inter players and management were due to join the rest of the travelling party at L’Anima, but cancelled their engagement at the last minute as Mourinho wanted his team fully focused on football.
Instead he insisted the players dined privately together at their hotel - Park Lane's five star Grosvenor House hotel, before having an early night.
A L'Anima source told Goal.com: “It was great to have the Inter family here but we were looking forward to hosting the team too. Some of the waitresses were keen on meeting Jose Mourinho so they were a little disappointed."
This is not the first time Mourinho has fallen out with one of his players. While at Chelsea he also endured difficult relationships with William Gallas, Andriy Shevchenko and Hernan Crespo. This latest saga is certain to lead to increased speculation that Balotelli will leave Inter this summer.
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