Scrumhalf was injured just nine minutes into the win over Italy on Sunday.
Six Nations: England's Ben Youngs set to miss Wales clash due to knee injury
England scrumhalf Ben Youngs is likely to miss the Six Nations clash against Wales at Twickenham next weekend after suffering knee ligament damage in Sunday's victory over Italy in Rome.
Youngs was injured just nine minutes into the 46-15 victory on the opening weekend of the Six Nations when his left leg was trapped as he passed from the back of a ruck.
A full assessment of the injury was to be carried out on Monday with a chance that he also might be out for the entire championship.
"He's unlikely to be available for the Wales game. It's too early to make any sort of prediction. I'm always optimistic," England coach Eddie Jones told reporters.
England would also name as replacement on Monday, officials said.