The 27-year-old was unable to complete the Selecao’s first full session after gathering ahead of the Copa America
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.
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.
Before then Brazil will face Qatar on June 5 and Honduras four days later in a pair of friendlies, before taking on the Bolivians, Venezuela and Peru in Copa America group play.
For Neymar, the injury could represent yet another setback after a frustrating club season that saw him play in just five games with PSG after his April return from a foot injury suffered in January.
Despite the injury, Neymar still finished tied for fifth in the Ligue 1 scoring charts with 15 goals.
The 2018-19 campaign was the second straight season in which Neymar has been hampered by a foot injury, with a different metatarsal problem knocking him out of the last three months of his debut campaign with PSG in 2017-18.
Neymar was able to return for last summer’s World Cup, where he scored two goals in five games as Brazil were knocked out by Belgium at the quarter-final stage.
The Selecao will look for redemption at the Copa America this summer, but they will not be captained by Neymar even if the attacker does return to fitness ahead of the tournament.
On Monday the CBF announced that manager Tite had stripped Neymar of the captaincy and instead handed the armband to his club team-mate Dani Alves.
Neymar had only been named permanent Brazil captain by Tite in September 2018, but he has now been replaced by his 36-year-old compatriot.