Forward Edin Dzeko suffered a calf injury in the warm-up at the King Power Stadium and skipper Vincent Kompany suffered a recurrence of a hamstring problem 77 minutes into his comeback.
Dzeko joins fellow strikers Sergio Aguero and Stevan Jovetic on the sidelines and there is little chance of any of them being fit in the next fortnight.
Kompany might also be out of action until the new year.
Manager Manuel Pellegrini said: "It is difficult immediately after the game to know what happened to both of them.
"Vincent Kompany has the same problem in his hamstring he had a few weeks ago, that is one of the reasons he didn't play on Wednesday in Rome.
"Edin Dzeko felt a muscle injury in his calf
Maybe he will also be a couple of weeks out
I think it is impossible (for him to return) before the new year.
"We will see with Vincent how hard his injury is but I think it will be very difficult for them to play before the next year."
Dzeko had made only two appearances since returning from another calf injury while Jovetic, who was a substitute in Wednesday's Champions League win at Roma, has had niggly hamstring issues in recent weeks.
Pellegrini said: "Jovetic also has a problem in his hamstring after the game against Rome
It is not a very important injury but I think he will also need a couple of weeks."
Top scorer Aguero damaged knee ligaments in last weekend's victory over Everton and could be sidelined for up to eight weeks.
The problems forced Pellegrini to draft 18-year-old forward Jose Angel Pozo into his starting line-up at Leicester and the youngster could now get further chances.
Pellegrini said: "We will see with Jose Pozo
We have other young players in the squad Patrick Vieira manages
We will see also another way to play but we are not going to complain about injuries."
The injuries marred City's latest victory in their Barclays Premier League title defence, although their performance was far from a convincing one.
Pellegrini's men looked lethargic after their Champions League exertions and only another goal from on-loan former England midfielder Frank Lampard separated the sides.
Lampard has now scored six goals since joining the club on a short-term loan from sister outfit New York City and his latest display is likely to increase Pellegrini's desire to extend the deal beyond December.
Pellegrini said: "There have been no serious discussions, but we know exactly what we must do.
"Frank wants to stay, we want to keep him
Now we must resolve the problem with New York City and MLS.
"He is very important
One of the reasons why he played today was because he has scored for me
Frank has been very useful for us in this moment."
Bottom side Leicester made life difficult for the champions in the early stages and City were generally below par.
Pellegrini said: "It was not a beautiful game for the fans, but I don't remember Joe Hart had any problems in our goal.
"Leicester did not really have any chances because we defended well
I don't think we played well, but it was not the target to play well in this game because it is very difficult to play with Leicester with 72 hours to recover from the last game and also after we had to fly back from Italy."
Leicester boss Nigel Pearson was pleased with the efforts of his side, even if they counted for little.
He said: "It was a disappointing result for us, one that I don't think we necessarily deserved, but we have got to deal with it - move on
There is not a lot we can do about it now.
"I was very pleased with the performance, but what we are looking for is results.
"Unfortunately we have been unable to break them down
Games like that when you can't break teams down, you have got to keep a clean sheet.
"We were undone just before half-time and that remains a frustration for us."
Pearson, who was recently involved in an exchange with a disgruntled fan, received some good backing from supporters.
He said: "I am not dismissing that, it is positive, but the important thing is the supporters stay behind the players
My philosophy is always to continue working in the way I feel is right.
"It is clear people have been frustrated with how things have gone in the last couple of months but I think it is too easy to over-emphasise the negatives
The performance today is something to be encouraged by."
Pearson was puzzled by and played down the significance of a picture of a fan apparently being ushered away from him by a steward early in the game.
He said: "I think that was David Nugent's dad
People may be trying to exploit potential situations to expand on something that happened last week
Quite frankly, I'm not interested."
Source : PA
Source: PA