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The Brazil international had only just been given the green light to return to action by the Catalan club's medical staff, after recovering from the back injury he picked up at the World Cup, but is now facing another spell on the sidelines.
"The club's medical team has indicated that his return to training will depend on how the injury treatment evolves.
"It’s worth recalling that, last Monday, Neymar Jr. received his medical discharge from the back injury that he suffered during the World Cup in Brazil."
Neymar made 26 La Liga appearances last term, scoring nine goals in the process, but his campaign was plagued by fitness problems.