Knee surgery for Kruis
It is expected that the second row will require a 10-12 week rehabilitation period.
Meanwhile, Mako Vunipola will join up with England this week and will continue his rehabilitation from injury.
A total of 32 players assembled at Pennyhill Park on Sunday to train for Saturday's Six Nations game against Wales at in Cardiff.
England started their Six Nations campaign with a 19-16 win over France at Twickenham, while Wales bagged a 33-7 win over Italy in Rome on Sunday.
England squad:
Forwards: Jack Clifford, Dan Cole, Charlie Ewels, Ellis Genge, Jamie George, Teimana Harrison, Dylan Hartley, James Haskell, Nathan Hughes, Maro Itoje, Joe Launchbury, Courtney Lawes, Joe Marler, Matt Mullan, Kyle Sinckler, Tommy Taylor, Mike Williams, Tom Wood.
Backs: Mike Brown, Danny Care, Elliot Daly, Owen Farrell, George Ford, Jonathan Joseph, Alex Lozowski, Jonny May, Jack Nowell, Henry Slade, Ben Te'o, Anthony Watson, Marland Yarde, Ben Youngs.
