Bath's Charlie Ewels has been called up to replace the injured Courtney Lawes in England's 25-man training squad named on Monday.
The squad will assemble in Oxford this week as England prepare to get their Six Nations campaign back on track following their 21-13 defeat against Wales on Saturday.
Lawes left the field late in the second half of that loss, and the RFU issued a statement on Sunday that said: "Courtney Lawes (Northampton Saints) will miss the rest of the Guinness Six Nations due to a calf strain sustained yesterday in Cardiff. Following the results of his scan this afternoon, Lawes is expected to be out for a minimum of four weeks. He will return to his club for rehabilitation."
It is a further injury blow for England one day after it was announced Dylan Hartley will undergo knee surgery on Tuesday, with the hooker likely to be out for up to 12 weeks according to Eddie Jones.
Ewels, who featured in all four of England's autumn internationals last year, is one of three players included in the squad who did not feature in Cardiff; Wasps' Nathan Hughes and Worcester's Ben Te'o the other two.
Maro Itoje has not been named in the squad but will continue his rehabilitation in Oxford according to the RFU, though Jones has hinted he may fast-track the Saracens man back into action.
"(Itoje) is coming along well," Jones said. "I might have to give him the hurry-up, because we've lost Courtney."
Meanwhile Bath pair Sam Underhill and Anthony Watson will be in for medical checks only.
England host Italy at Twickenham on March 9 before playing Scotland on March 16 in their final game of the tournament.
England's 25-man training squad
Forwards: Luke Cowan-Dickie, Tom Curry, Charlie Ewels, Ellis Genge, Jamie George, Nathan Hughes, George Kruis, Joe Launchbury, Ben Moon, Brad Shields, Kyle Sinckler, Billy Vunipola, Harry Williams, Mark Wilson.
Backs: Joe Cokanasiga, Elliot Daly, Owen Farrell, George Ford, Jonny May, Jack Nowell, Dan Robson, Henry Slade, Ben Te'o, Manu Tuilagi, Ben Youngs.