Mancini was relieved of his duties on May 14, exactly a year after he claimed City's first Premier League title in 44 years following a dramatic final-day victory over QPR.
The 2012-13 campaign saw the club struggle to keep pace with eventual champions Manchester United, however, with Mancini's side also crashing out of the Champions League group stages for the second season running, as well as losing out to Wigan Athletic in the FA Cup final.
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"I lost the FA Cup, in football it can happen," Mancini told Corriere dello Sport. "It was a bad day for the whole team. But I never expected what happened. I never believed that the rumours about [Manuel] Pellegrini were true. Two months after my sacking, I still don't understand the reasons and the timing.
"I think I deserved more respect for what I've done at City in three-and-a-half years. The club didn't win a title for 40 years, I won a Premier League, an FA Cup, a Community Shield and, in the worst season, I lost a final and finished second in the Premier League.
"The numbers are clear, my sacking still doesn't have a reason. I'm proud of my work. I'm not angry with [City owner Sheikh] Mansour and [City chairman] Khaldoon [Al Mubarak]. They are two great managers and I'll always be grateful."
Mancini also launched a scathing attack on City chief executive Ferran Soriano, suggesting the former Barcelona general manager became frustrated with the Italian's influence within the club and that the pair did not see eye-to-eye on football matters.
"Soriano? For him I was too big within the club," he added.
"A manager in full control, loved by the fans still today. He judged a person and a context without knowing nothing of the people he should have dealt with. I never thought of him as an interesting person from a football perspective, we never spoke the same language.
"And I'm not talking about Italian, Spanish or English. His past at Barcelona? I think he was coming from an airline. I've been in football since I was 13 and I had never heard anything about Soriano. He arrived in England with his manager role and I saw that he loves to speak, to get media exposure."