City will begin their defence of the Premier League away to Newcastle United on Sunday but Mangala, who signed on the dotted line on Monday, will not be involved.
The 23-year-old central defender has been training on his own at City's base in Carrington as the Premier League club finalised payments to third parties with a stake in Mangala to complete the transfer from Porto.
Due to that limbo period where he was unable to train with either Porto or City, the France international admitted he will not be ready to play at St James' Park.
"I think that I will need a bit of time in order to be 100 per cent but it is normal," Mangala said.
"It is like those who returned to training last week. But I will work hard in order to be 100 per cent as soon as possible.
"I went on a run every day and trained in the gym. Holidays are great but if the time is too long, it is difficult to come back."
Mangala was part of Didier Deschamps' France squad at the World Cup but did not get on the pitch.
The Paris-born centre-back knows by missing the opening game of the league campaign he will have to work hard to break into City's starting XI, despite his £31.9 million transfer fee making him the most expensive defender in British football history.
"I will work hard to try to have a spot in the starting XI but the most important is that the team win the games, win titles," Mangala said.
"It is my main goal - work in order to help the team to win as many titles as possible."
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