England number eight Billy Vunipola has been ruled out for the remainder of this year's Six Nations tournament with an ankle injury.
Vunipola suffered the injury during England's dramatic 13-10 victory over Ireland on Saturday, limping off in the first half following a tackle by Ireland lock Devin Toner.
A scan revealed that the 21-year-old has suffered ligament damage and will not be able to feature in either of the two remaining games against Wales and Italy.
"It is a blow as Billy has had a good Six Nations but he is young and will be back," England head coach Stuart Lancaster told reporters.
"The encouraging thing is we have got Ben Morgan and other back rows such as Matt Kvesic and Tom Johnson, who are all competing hard for places."
England would complete their first Triple Crown for more than a decade if they beat Wales at Twickenham on March 9.
