Chelsea will be without midfielder Frank Lampard against Manchester City on Saturday and possible for a further two matches.
Lampard is understood to need more time to recover from his recent hernia surgery and so will miss the trip to Eastlands along with striker Salomon Kalou and midfielders Yossi Benayoun and Gael Kakuta.
He is doubtful for Chelsea's Champions League group fixture against Marseille in midweek and their crucial Premier League match against Arsenal at Stamford Bridge the following weekend.
Kakuta (back), Kalou (thigh) and Benayoun (calf) were all injured during Chelsea's 4-3 Carling Cup exit at the hands of Newcastle on Wednesday night. But Lampard is the biggest blow as the England midfielder had been widely expected back in time for their first real test of the season against Roberto Mancini's side.
Meanwhile, striker Didier Drogba insists he and partner Anelka are just as good at setting up goals as scoring them as they prepare for the trip to Eastlands.
"There are players in our team who can score goals but those same players are capable of giving assists,'' said Drogba. "It helps if I can go outside to the right or left to make some space and I know that Nico (Anelka) or Florent Malouda will move up front in that situation. They both show that understanding and the desire to score goals, so it makes things really interesting.
"We know we have the quality in the dressing room to make the difference at any time in any game. This is going to be important in tight games because our opponents will know that a chance could come from a good pass by a striker or by a good strike from a midfielder.
"It's good to have so many players with these qualities and to be able to make goals from different situations. The fluidity comes because we know each other so well now and that makes things easier for you on the pitch. That understanding is there because we've been together such a long time so we know more or less what we have to do.''