The France international has been sidelined since suffering knee ligament damage in a tackle from Newcastle's Mapou Yanga-Mbiwa five weeks ago.
Nasri rejoined the squad for full training earlier this week and his return, after two games without a win, is timely ahead of next Tuesday's Champions League encounter with Barcelona.
The 26-year-old had been in fine form before being carried off on a stretcher at St James' Park, but manager Manuel Pellegrini does not want to build up his comeback.
Pellegrini said: "He is a very important player, it is impossible not to miss him.
"But we also had other injured players before him - David Silva, Sergio Aguero, Stevan Jovetic and Vincent Kompany - and we always managed to continue winning.
"In the last two weeks I said this was not an excuse because we have had a lot of injuries during the year.
"In the last two weeks maybe we have had injuries in the same position and that has been a major problem.
"Samir Nasri is a very important player and we always miss him, but with the squad we have I think we can also win without him."
Two other key players in top scorer Aguero and midfielder Fernandinho remain on the sidelines but Javi Garcia is also fit again after a muscle strain.
Pellegrini said: "I think it is very important to have players, Samir Nasri and Javi Garcia, fit for this game. It is very important for us.
"(Matija) Nastasic, Fernandinho and Aguero are not fit for this."
City had an unexpected night off on Wednesday as their Barclays Premier League clash with Sunderland was postponed due to inclement weather.
That could affect his team selection for the visit of Chelsea but, with the Barca encounter also at the forefront of his mind, he is cagey about revealing his thoughts.
Speaking at a press conference to preview the match, the Chilean said: "Tomorrow we will see the 11 starters."