England lock Courtney Lawes faces being out of rugby for 12 weeks after suffering a pectoral injury.
The Northampton forward, who has won 87 caps, was hurt during England training last week.
His Saints team-mate David Ribbans has been called into England's Guinness Six Nations squad to bolster second-row resources ahead of their remaining games against France and Ireland.
Northampton said that Lawes will undergo surgery and he faces an approximate 12-week recovery period.
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That would sideline him until late May or early June, meaning he will miss the overwhelming majority of Saints' remaining Gallagher Premiership fixtures.
Whether it affects his British and Irish Lions squad selection hopes to face South Africa this summer remains to be seen.
"Northampton Saints can confirm that, following consultation between the club's medical staff and a specialist, Courtney Lawes will undergo surgery on the pectoral injury he sustained in England training last week," Saints said in a statement.
"The 32-year-old lock will require a rehabilitation period of approximately 12 weeks."
England resume their Six Nations campaign against France on Saturday week, having suffered defeats against Scotland and Wales either side of beating Italy.
The Rugby Football Union, meanwhile, added that some of Jones' 28-man squad "who have received less playing time during the tournament" will be given an opportunity to play for their clubs this weekend.
"This will be an individual decision for each player from a performance perspective and is in line with tournament regulations and Covid-19 protocols," the RFU said.
Jones limited his Six Nations squad selection in January to 28 players in an effort to enhance coronavirus safety measures.
The RFU struck an agreement with Premiership Rugby and the Rugby Players' Association that enables the 28 members to remain in camp for the entirety of a Test week.
It was previously customary for Jones to pick an initial training squad of around 32 players that would arrive in camp on a Monday.
This would then be trimmed to a smaller group of 23 to 25 on a Tuesday or Wednesday night, enabling those not in contention to play for England that weekend to turn out for their clubs instead.
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