Vasco da Gama fans stormed into the team's training base less than 24 hours after a 2-0 defeat to Goias that left them in deep trouble at the bottom of the league.
With nine games remaining, the Brazilian side are third from bottom in a league where four teams are relegated.
Around 50 fans are believed to have taken part in the protest, with some running into the dressing room as the team prepared for training and others shouting abuse from the terraces.
Once the police got the situation under control, a group of fans were allowed to voice their concerns to manager Dorival Junior.
According to Reuters, Vasco fans have threatened violence if they lose this Sunday's Rio derby with Botafogo.