Everton defender Ramiro Funes Mori is expected to be out for six to nine months after undergoing knee surgery in Barcelona.
He suffered a meniscus tear while playing for Argentina against Bolivia in March, an injury which curtailed his season at Everton.
Now he has undergone surgery in Spain and is set to miss the bulk of the coming season.
A statement on the club's website read: "Ramiro Funes Mori has had a problem within his knee and has undergone further surgery which will require prolonged rehabilitation of a minimum of six to nine months."
Funes Mori, who started 16 league games last season, would have been expected to provide cover for new signing Michael Keane, Ashley Williams and Phil Jagielka at the back while also having the capacity to slot in at left-back if required