Former England captain Chris Robshaw was among the Barbarians players to breach Covid code of conduct.
The flanker and 11 others left their London hotel on Wednesday night; Robshaw was due to make farewell appearance before moving to San Diego.
Saracens stars Richard Wigglesworth, Jackson Wray and Sean Maitland were also reportedly part of the group.
It’s thought that the Baa-Baas have let go all 12 players and are urgently looking for replacements.
A decision is to be made by Friday 3pm on whether game can go ahead.
In a statement, the RFU said: “On the evening of 21 October a number of Barbarians players breached the agreed Covid code of conduct protocol by leaving their hotel bubble without permission and without informing organisers about their whereabouts.