The Argentine was taken off during the Blues' last match before the international break, and was expected to be out for two weeks.
However, the Italian has said that he will definitely feature in their Champions League game against Villarreal on Tuesday.
"Sergio could be ready for Saturday but I don't know if we will take the risk," he told the club's official website.
"I am sure 100% for Villarreal on Tuesday."
City are currently second in the Premier League table on goal difference behind local rivals Manchester United.