The French defender completed his move to City from Porto earlier this week, but a lack of a pre-season has left him playing catch-up in terms of fitness.
"I think that I will need a bit of time in order to be 100% 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."
The centre-back was part of the France squad that travelled to the World Cup this summer.