The England international has been ruled out of Saturday's Barclays Premier League date with Newcastle at the Etihad Stadium and will be assessed before Tuesday's glamour encounter.
Milner, impressive this season in various positions, has taken a knock and although City are hopeful it is not serious, they are still to learn the extent of the problem.
Manager Manuel Pellegrini said: "We will see
It is not very, very serious but he couldn't work in the whole week, so we will see how he improves in the next (few) days but he has a kick in his ligament in his knee.
"He is not available for tomorrow
All the other players in the squad are fit."
Attention is already starting to turn to the visit of Catalan giants Barca, but with a seven-point deficit to leaders Chelsea in the Premier League to make up, Pellegrini wants to keep focus on Newcastle.
The Chilean is so keen to prevent the Champions League becoming a distraction that a planned player interview session for Spanish-speaking media to preview the game on Thursday was cancelled at short notice.
This attracted some negative coverage in the Spanish press but Pellegrini has promised to rearrange.
He said: "It was nothing important
I think it was not the right day to have a press conference about a game that we must play on Tuesday.
"I think it is more important to finish with Newcastle and then we can do a press conference on Sunday or Monday."
New signing Wilfried Bony is in contention to make his City debut against the Magpies.
The £25million striker has not been available since being signed from Swansea last month due to his involvement, along with key City midfielder Yaya Toure, in Ivory Coast's African Nations Cup triumph.
Bony finally linked up with the City squad earlier this week and is set to be included in the squad, although Pellegrini was offering no guarantees.
He said: "I think that Bony will be an important player for us
He will be in the squad list but we will see if he will be in the starting 11 or have some minutes after that
He has worked with our team the whole week without any problems."
City want to build on their Stoke victory, which ended an indifferent run of five games without a win
Pellegrini said: "It is important for us to try not to think about where Chelsea are or the other teams
It is important for us not to drop points but the only way to do it is to play well.
"But I always say Newcastle is a very good team, they have very good players
It is not easy to play against them."
Newcastle head for City with their defensive resources stretched to the limit by injury
Left-back Paul Dummett (knee) is facing up to 12 weeks on the sidelines alongside long-term casualty Steven Taylor (Achilles), leaving head coach John Carver with just four fit senior defenders, Daryl Janmaat, Mike Williamson, Fabricio Coloccini and Massadio Haidara.
Carver has problems in midfield too with Remy Cabella having damaged a knee in training to join Siem de Jong (collapsed lung) and Cheick Tiote (knee) in the treatment room, although the Frenchman's injury is relatively minor.
Despite those problems, Carver is confident of getting something out of the game given their impressive Capital One Cup result at the Etihad before Christmas.
"We are going there knowing that we are playing against a good side, but we are not going to be fearful because we've proved that we can go there and get a result," the boss said.
"Yes we played them at the start of the season and lost the game, but we were in the game for long periods of time
It was because we were on the front foot trying to get the equaliser that we got caught on the counter attack.
"We know that City have a huge Champions League game coming up on Tuesday against Barcelona, so what changes (Manuel) Pellegrini will make, I'm not entirely sure.
"One thing I will say is that City don't just have a good starting 11, they have a strong second string as well, so picking a first 11 must be difficult."
Source : PA
Source: PA