Bellamy, who is expected to be left behind when City's first-team fly to Los Angeles for a pre-season tour on Friday, revealed that Mancini tore up Bellamy's personalised training regime when he took over from Mark Hughes at Eastlands.
"It was tough [when Hughes left], it felt like losing someone,'' he told the Daily Telegraph. ''It was probably as bad as losing a family member in some ways, I even struggled to eat for a few days.
"It was a totally different structure [under Mancini] which affected me completely. Mancini told me to stay with the team all the time. We had longer training sessions, but with no intensity whatsoever.
"He seemed to know my knee better than I knew it myself. He tried to explain why I had problems with it, and what I should do about it. When I told him that my knee was hurting, he tried to tell me it wasn't.
"Mancini wanted me to come in another day and do some work, but I told him that I'd finished my work that day, that I was keeping to my own schedule. That was when he started about my programme, that I couldn't follow my own schedule while he was the manager, and that I had to do what he was telling me.
"He said, 'If you don't, you can go back home now. And don't come back in again'. I replied, 'Okay, no problem, I'm going home then'. That was a week after he'd arrived, and then he never spoke to me again.
"When I went into pre-season, the physio, Jamie Murphy, spoke to Mancini and told him that I wasn't able to do a lot of the things that Mancini wanted, because it would cause a reaction to my knee. Mancini wants to have it all."
Bellamy, 31, who spent last season on loan at Cardiff City, has no intention of reducing his £80,000-per-week wages in order to engineer a move away from Eastlands, where his contract expires next summer.
"To be honest I don't want to go on loan again, because where would I go after that?" Bellamy added. "After another loan period my options would be probably reduced. A permanent move would be somewhere best, but it would have to be somewhere wealthy, so I can guarantee future earnings for my charity, but that would be difficult with my current wages.
"If they [City] pay me the final year of my wages, then I'm sure I can go wherever I want. In that case, my first option would be to Cardiff, to give it another go. But it has to be feasible, the financial health of the club is the most important thing.
"No chance [of reducing wages], that is impossible. I have my own academy [in Sierra Leone] where I have to take care of 13 children, day in, day out. My wages are more important to them than they are for me.
"City are the richest club in the world. They work to a budget that no-one else works to, so they can write their own rules. Right now the club has got itself in a situation where a lot of players have to go on loan.
"Obviously it all depends on Manchester City. At present, I expect to go back there and stay the whole year. And if Roberto Mancini is still there, I'll do probably very little, obviously I won't be involved with him and the first team."