Barcelona forward Neymar has suffered an injury during international training with Brazil in Seoul on Thursday, according to the Seleção Brasileira Twitter page.
The 21-year-old will be sent for a scan to determine the extent of the damage, after doctor Edilson Thiele told the Brazilian UOL website that it was too early to make an official diagnosis on the injury.
Neymar fell to the ground after a challenge with Lazio midfielder Hernanes, and received treatment from physios on the pitch before leaving the field unaided.
The Barca star must now be doubtful for his country's international friendly against South Korea on Saturday, and it remains to be seen whether he will return in time for the match against Zambia next Tuesday.
Neymar has been in impressive form for Gerardo Martino's side in 2013/14, in his debut campaign at Camp Nou.
With two goals and five assists in just seven La Liga appearances, the former Santos star's absence will come as a huge blow for Barcelona, and officials in Spain will be keeping their fingers crossed for a positive outcome from the scan.