England captain Owen Farrell will miss the entire Six Nations after having surgery on an ankle injury later on Wednesday.
Farrell, who has not played since limping out of England's win over Australia in November was set to make his comeback in Saracens' game against London Irish last weekend.
However, he was injured in a training-ground collision in the build-up to that match.
Saracens said they are expecting Farrell to be out for eight to 10 weeks.
More to follow.