Manchester City defender Aleksandar Kolarov could be out for six weeks after scans showed his ankle injury is worse than was initially feared.
The left-back damaged ankle ligaments in Saturday's goalless draw against Tottenham and could be sidelined until October.
Meanwhile, boss Roberto Mancini does not expect Thursday's Europa League clash against Romanian side FC Timisoara to be easy.
He said:"It is a difficult draw because everyone expects us to progress but we have watched Timisoara and they are a hard-working side who will see us a great possible scalp.
"You have to be patient and remember that there are two games in this tie.
"I always think that the first game in any European competition is the hardest and we are still in the very early stages of my players becoming a team. Timisoara have already played four league games and two in the Europa Cup.
"I have plenty of options for the game but, at this stage of the season, I want to give as much chance as possible to new players to settle into the team and learn about each other so we can grow as a group. It is a balance between that and making sure that certain players do not become overused or tired.
"It is an important game because we want to progress in every competition and there is no room to play less than 100 per cent. The main thing is to ensure that the score after the second game at the City of Manchester Stadium is in our favour."