Chris Robshaw, Richard Wigglesworth, Sean Maitland and Jackson Wray are among 12 Barbarians players stood down from Sunday's fixture against England after breaking Covid-related rules.
The players left their hotel bubble contrary to team protocols to have dinner at a central London restaurant.
Sunday's game is in the balance as the Barbarians try to recruit enough players to replace those stood down.
However, indications are that they remain confident of raising a team.
As well as Wigglesworth, Wray and Maitland, it is understood a number of other Saracens players were also involved.
Barbarian FC expressed their "extreme disappointment" in the conduct of the players who breached the regulations.
They had only announced their 23-man squad on Wednesday and face a considerable task replacing those expelled.
Cardiff RFC said on Friday
that centre Max Llewellyn, son of former Wales lock Gareth, and full-back Ioan Davies had been called up to the squad.
An update on whether the game can go ahead is expected later on Friday.
The players involved in Wednesday night's unauthorised excursion were kept separate from the rest of the Barbarians squad on their return to the hotel.
Although the team are due to be tested for coronavirus again before Sunday's match at Twickenham, the Rugby Football Union stated it would "not be possible to guarantee that these players are not infectious in the period up to and including the match".
"The RFU scheduled the fixture to provide a warm-up game ahead of the postponed Italy v England Guinness Six Nations decider, however, it will not compromise the safety of players to do so," it added.
The build-up to Barbarians games is famous for its focus on socialising and the team management installed a team-room in their London base to keep the players entertained.
Leicester wing Nemani Nadolo, who has played twice for the Barbarians, and Bristol Bears, who had been on standby to take part in Saturday's Premiership final before Wasps were shown to have contained a Covid-19 outbreak, were among those to offer their services to the Barbarians on social media.