River, record 33 times league champions, lost 2-0 against Nacional B side Belgrano in Cordoba on Wednesday in the first leg of a play-off. They need to finish level on aggregate to stay in the top flight.
Fans clad in River's red and white colours screamed insults at players and club president Daniel Passarella and demanded the head of coach JJ Lopez. They squared up to police outside the empty stadium and also hurled insults at reporters.
After flying back from Cordoba on Thursday, River headed straight for Hindu rugby club outside the capital looking for quiet to prepare for Sunday's home second leg.
About 500 fans also gathered outside Hindu to vent their anger at what they perceive to be a lack of commitment from the players. Some fans carried a banner that read: "Kill or die."
Wednesday's match was interrupted for 20 minutes after River fans broke through perimeter fencing and onto the pitch to remonstrate with their own team's players and demand more effort after they had fallen two goals behind.
River are paying for years of mismanagement on and off the pitch which has left them with a low three-season points average with which relegation is decided in Argentina's top flight.
Passarella, widely criticised for not going to Cordoba, was at Hindu with the squad while the club issued a statement saying he would give a news conference next week to explain how the administration his board succeeded 18 months ago was responsible for the club's disastrous state.
