Manchester City midfielder David Silva is likely to miss three to four weeks with a knee ligament injury, which rules him out of this weekend's derby match against Manchester United at the Etihad Stadium.
Midfielder Yaya Toure also picked up a groin problem in the League Cup defeat to Newcastle United, but he is expected to be available for Sunday lunchtime's game.
Silva will also miss the crucial Champions League clash with CSKA Moscow at the Etihad Stadium, along with the Premier League clash against Queens Park Rangers at Loftus Road next week.
He could return at the end of November for the home game against Swansea City in the Premier League on November 22, and potentially huge Champions League showdown against Bayern Munich three days later - but that remains uncertain.
City would at least expect him to be available for the visit to Southampton on November 30.
Manager Manuel Pellegrini said: "He is a very important player but I always say the same thing, we have a squad. We have to replace him with another player because every team has different problems with their players.
"Yaya Toure has a small problem. We'll see tomorrow but I think he will have no problems to play."
Commenting on Sunday's game with United, Pellegrini told his pre-match press conference: "On Sunday it will be City v United and last year was the same. It was not me v Moyes and this time it's not me v Van Gaal.
"For supporters it's a special game and we know that. We know what it means to win against Manchester United."