England prop Mako Vunipola's participation in the Six Nations Championship is in doubt.

Vunipola suffered suspected ligament damage in his left knee after being forced off in Saracens' European Champions Cup win at Sale last weekend.

The 25-year-old is expected to see a specialist in the next fortnight when the swelling on the knee subsides.

But Press Association Sport understands that his club Saracens have put a time frame on Vunipola's potential absence as between four to 12 weeks.

If a scan highlights minimal damage, then Vunipola should be fit for England's Six Nations opener against France at Twickenham on February 4.

But a more serious injury could rule Vunipola out of the entire tournament and prevent him from being part of England's title defence.

That would be a huge blow for England coach Eddie Jones as the 39-times capped Vunipola has played a major part in the team's success during 2016.