Gabriel Jesus had to be stretchered off the field towards the end of Brazil's 1-0 defeat by Argentina after being struck by Manchester City team-mate Nicolas Otamendi.
The attacker started the friendly in front of 95,000 fans in Melbourne and missed an open goal before picking up an injury late on.
As Jorge Sampaoli's Argentina resolutely defended their 1-0 lead, Brazil's Jesus competed for a header but was struck in the side of his head, close to his eye, by the flailing arm of Otamendi.
There was nothing malicious in the challenge but the 20-year-old was in some clear discomfort as he fell to the turf following the knock.