Neymar limped out of Brazil training on Tuesday, with the 27-year-old appearing to have suffered an injury to his left knee.
While attempting a shot Neymar came off favouring his knee and, after trying to continue training, he eventually was forced to limp off the field alongside team doctor Rodrigo Lasmar.
According to the Brazilian Football Confederation (CBF), Neymar has already begun treatment for the injury and will remain under evaluation.
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The injury will be a major concern for the Selecao as they get ready to host the Copa America, with their opening match set to take place against Bolivia in Sao Paulo on June 14.