The young midfielder has suffered minor injuries after being punched and kicked inside the Sao Paulo-based side's official shop by members of an organised supporters' group
Police say the 23-year-old was seen arriving at the official club store before becoming the target of a serious attack, in which one of Palmeiras' organised fan groups collectively proceeded to punch and kick him.
Club lawyer Andre Sica also commented on the incident, claiming on local television that Vitor and his friends were originally confronted by angry supporters, who expressed their disappointment at the club's poor recent form before it escalated into a physical altercation.
Vitor was soon admitted to the nearby Sao Camilo hospital, where he was treated for his injuries. He did not suffer any lasting damage, but the attack forced Palmeiras into postponing Wednesday's fixture against Flamengo.
Former Brazil striker Ronaldo has also taken a stance on the matter, expressing his anger through his Twitter account, while also confirming that no arrests had yet been made.
"It's absurd what happened to the player, Joao Vitor of Palmeiras! I have more than sympathy [for Joao], I am outraged at the assault. While no-one has been arrested, tried or condemned, attacks on players will not end," he said.
Organised fan groups are common in Brazilian football. They are known for their violent encounters with the police and other groups of supporters.
CSKA Moscow striker Vagner Love was also the victim of a fan group's dissatisfaction when he was forced out of Palmeiras in 2004 after receiving death threats.