Pep Guardiola director confirmed that Manchester City defender faces up to 10 weeks due to a thigh injury.
Switzerland has learned that he needed surgery after being forced in the first half during the Champions League in the city against Real Madrid on Tuesday.
Guardiola said he expected the player to come out “from eight to 10 weeks.”
He added: “We only wish the best recovery for Mano. The effort he made this season was incredible.”
Midfielder Jacques Grilliche is also suspicious of the Premier League clash on Saturday against Newcastle with a thigh problem.
Grealish only lasted 30 minutes against Real, but Guardiola hopes the injury is serious.
He said: “It is not difficult as Manu did, but I don’t know if he will be prepared tomorrow. I don’t think that, but we will evaluate it.”