"Didi kicked a ball in training yesterday (Monday) with the end of a toe and unfortunately it looks like he may have ruptured a tendon," City manager Mark Hughes told the club's official website.
"He will go over to Zurich today to see a surgeon that he has seen with a similar injury before.
"The feeling is that it is the same thing that has happened before.
"The best case scenario is that it will be nine weeks, but it could be twelve.
"Obviously it is a blow for Didi, we are a bit light in midfield areas so we could have done without this.
"Until the surgeon look at him we can't say whether we may have better news on it."