Barcelona striker Sergio Aguero will be out for 10 weeks because of a right calf injury, say the La Liga club.
In a statement, Barca say tests on the Argentine forward have confirmed a tendon injury.
He spent 10 years at City, during which time he became the club’s all-time leading goalscorer with 260 goals in 390 games.
Aguero won the Copa America this year with Argentina, alongside Lionel Messi, who has confirmed his departure from Barca.
Speaking at the time of his move to Spain, Aguero said: “We all know that Barcelona are the best club in the world.
“I think I made a great decision to be here and of course it is a step forward in my career.”