The €40 million signing from Porto had to train alone while in limbo between the two clubs and confirms that he will not be "100 per cent" for the team's first Premier League game
City will begin their defence of the title away to Newcastle on Sunday but the centre-back, who completed his €40 million move from Porto on Monday, will not be involved.
The 23-year-old 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 and that limbo period has seen him fall somewhat behind on full match readiness.
"I think that I will need a bit of time in order to be 100 per cent but it is normal," the Frenchman told the club's official website.
"It is like those who returned to training last week but I will work hard in order to be 100% 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.
"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. It is my main goal - work in order to help the team to win as many titles as possible."