Tevez had moved to United on a two-year loan deal in the summer of 2007 after a stint at West Ham.
A £25.5m fee had been agreed at the time if United wanted to buy the player from his advisors, who owned his economic rights, and make the move permanent.
Tevez believed he was kept waiting too long for a deal to materialise and, in the meantime, was unhappy at his treatment by the Old Trafford outfit as well as his lack of first-team opportunities.
The two eventually parted company when Tevez rejected a five-year contract from United earlier this summer in favour of a move to their local rivals.
But Ferguson said on Monday: "I half expected Tevez would be going a long time back.
"I think he maybe did a deal around January because I spoke to him and gave him an offer on the night we played Inter Milan (in March) and he never came back to me.
"I phoned him on holiday and he never got back to me and I texted him twice and he never got back to me then either, so obviously he had made his mind up a long time ago.
"He was a good player and did well for us. But he obviously assessed the situation and wanted to go somewhere else."
Tevez denied any suggestion a deal had been agreed with City in January 2009 as he praised the United supporters for their backing of him.
The Argentine built up a good rapport with United's fans as he helped the club to the 2008 and 2009 Premier League titles, the 2008 Champions League trophy as well as last season's Carling Cup.
He's always thrived under competition and strived to be number one wherever he goes
Tevez's advisor Kia Joorabchian
And Tevez added: "The fact I did not stay at United was not because of the fans.
"They must understand a part of my heart will always be with them. They were always extremely supportive, even when I wasn't playing."
Tevez's advisor Kia Joorabchian said his client would have no difficulty in crossing from the red half of Manchester to the blue.
"I don't think he has any bitterness. He thanked the United fans and club for his two years which he enjoyed very much," he told BBC Radio 5 Live.
"But we've seen throughout his career that he fights 100% the moment he puts the shirt on for that club."
With the likes of Craig Bellamy, Roque Santa Cruz, Benjani, Ched Evans, Felipe Caicedo, Valeri Bojinov and Robinho all fighting for places in City's forward line, Tevez is likely to face stiff competition for a regular role.
But Joorabchian said the battle for regular first-team action would inspire Tevez, rather than worry him.
"Carlos was not upset by the competition factor at United," he said.
"It was not that he wasn't playing because of his form. More that he was left out without any real understanding of why.
"He's always thrived under competition and strived to be number one wherever he goes."
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