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.
The setback came days after the club lost iconic Lionel Messi after failing to agree a new contract.
Aguero, 33, joined Barcelona from Manchester City on a two-year contract in June.
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 compatriot and team-mate 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.”