England have suffered a major setback after it was confirmed that Saracens number eight Billy Vunipola broke his arm against Racing 92 on Sunday.
Although no time frame has been given for his return, Vunipola is unlikely to play any part in the forthcoming Six Nations.
"Billy will see a consultant over the coming days to determine the full extent of the injury before undergoing rehabilitation," Saracens said
Vunipola's ball-carrying at number eight is one of England's greatest assets, forcing Jones to look at alternatives.
It could provide the opportunity for Tom Curry, a star of the World Cup and world player of the year nominee, to be joined in the 35-man squad by twin brother Ben, who also plays in the back row.
Another flanker who has been earning rave reviews this season is Vunipola's team-mate Ben Earl, a blockbusting openside who at 22 is a fixture in Saracens' back row.
Also lighting up Allianz Park has been wing Rotimi Segun, although he is operating in a competitive position.
How many additional Saracens players Jones is content to call upon remains to be seen, however, as the double winners come to terms with their automatic relegation from the Gallagher Premiership at the end of the season for breaching salary cap regulations.
While England can pick players competing in the Championship, there is no precedent for it and the club are seeking urgent discussions with Jones over his view on the matter.
It will be Jones' first England squad since the World Cup and the Australian stated in November following the defeat by South Africa in the final that the team that had excelled in Japan was "finished".
There will be few big-name casualties, however, considering the young age profile of the side, but veteran tighthead prop Dan Cole is unlikely to be present.
Uncapped Northampton full-back George Furbank is set to feature in the group that will travel to Portugal on Thursday for a pre-Championship training camp.
