A knee injury has ruled Owen Farrell out of England's entire Six Nations campaign.
It had been suggested that the fly-half may only miss next weekend's opening clash against Wales, having suffered the complaint during the European Rugby Champions Cup tie between Saracens and Clermont Auvergne on Saturday.
However, having had the problem assessed by a specialist, medial ligament damage has been revealed, which will keep Farrell sidelined for at least the next couple of months.
"It's a real shame for Owen that he sustained this injury and we wish him the best for his recovery," said head coach Stuart Lancaster.
"We are fortunate to have three other number 10s in the squad in what is a very competitive position."
The 23-year-old has made 29 appearances for England, from which he has contributed 290 points.
