Saturday 24 December 2016 14:31, UK
Mako Vunipola will see a specialist in the next two weeks to determine whether his Six Nations participation is in doubt.
The England prop injured his knee during Saracens' European Champions Cup win at Sale at the weekend and is yet to be fully assessed.
A full diagnosis will be made once the swelling subsides, but Vunipola has just five weeks to prove his fitness for England's opening game against France on February 4.
The 25-year-old played in every game of England's unbeaten year, helping them to a Grand Slam and a series whitewash in Australia under Eddie Jones.
Speaking after the Sale game, his Saracens boss Mark McCall said: "Mako has got a bit of soreness in his knee which will be assessed.
"Anybody would miss Mako Vunipola but we don't know how long he will be out for yet."
