The Belgian playmaker is expected to be out for eight to ten weeks with a medial ligament injury suffered against Everton in midweek.
He’ll be joined on the sidelines for the FA Cup fourth round tie by Wilfried Bony, Aleksandar Kolarov, Vincent Kompany, Eliaquim Mangala and Samir Nasri.
“We knew after the game it was a serious injury – not a season-ending injury as it was not a cruciate, but an important injury and will be out for 8-10 weeks,” Pellegrini revealed.
“We must continue playing with the whole squad if we want to be a competitive team. It’s an important player less but we must continue with optimism and give responsibility to the squad.
“Elsewhere, the same injuries as last week – Vincent, Mangala, Kolarov – I hope they will return next week to at least work with the squad.
“Eight to ten weeks more for Nasri and Kevin and I hope in a couple of weeks Bony will be fit again.
“It’s not our intention to bring in anyone in January. In some moments we couldn’t play with Sergio or David and now we play without Kevin.”
Pellegrini was also asked if he is targeting a four trophy haul this season.
City have progressed to the final of the Capital One Cup, are second in the Premier League, through to the Champions League quarter finals and will now aim for the fifth round of the FA Cup in Birmingham on Saturday.
Manuel ruled: “I don’t know if it’s realistic or not but we’re not thinking about that – just about Villa, then the next game.
“It’s important to continue being involved in all competitions and to show you’re a strong team in all of them.
“It was important for us to focus game by game, it’s difficult to play so many games.
“We have just one game postponed from the Capital One – if we continue in the FA Cup to the final we’d have at least two more games suspended so it’s difficult, if you continue in the Champions League, to find a day when you can play all those games.
“That doesn’t matter, we’ll have our mind on the FA Cup and try to advance.
“It’s the same team we play that we played in November – we started in Remi Garde’s first game. We drew against them in their stadium so I think tomorrow will be a similar game and very difficult also.”
Finally. Manuel was asked about what kind of reception Fabian Delph will receive on his second return to his old stomping ground...
“I don’t think that fans of Aston Villa will have changed their minds about Fabian Delph – he can expect the same reception,” Pellegrini added.
“He’s a professional player, every player has the option to take new options. He’s improved his career by playing in the Champions League.
“He’s important – he had a lot of injuries at the beginning but every player when he can play normally, their performance will improve to the level we know they can.”
