Peru striker Jefferson Farfan has been hospitalised with head trauma after a collision with a teammate during training.
The 33-year-old came off badly after a coming-together with one of the team's goalkeepers during training at their base in Khimki on Saturday.
Farfan, who plies his trade in Russia with Lokomotiv Moscow, is in a stable condition but still being closely monitored.
Peru's football federation stated that initial results "were favourable for the player", and that Farfan was transferred to the hospital after all medical protocols were followed on the field.
Los Incas have already been eliminated from the World Cup following 1-0 losses to Denmark and France in Group C, and take on Australia in their final game on Saturday.