Wasps duo Elliot Daly and Matt Mullan will not travel to Portugal with the rest of the England squad on Sunday after picking up injuries in a 38-22 win over Northampton Saints.
British and Irish Lions star Daly did not emerge for the second half of Saturday's Premiership clash due to an issue with his right knee.
Prop Mullan, meanwhile, left the field with an elbow injury in a match that also saw Northampton and England back Piers Francis forced off late on.
The RFU confirmed on Sunday that Daly and Mullan would stay behind when Eddie Jones' men head to Portugal for a period of warm-weather training ahead of November Tests against Argentina, Australia and Samoa.
"Mullan and Daly will remain with their club for treatment and will have scans over the next couple of days," read a statement.
No replacements have been called into the squad at this stage.