Moody, 32, has led England since the end of last year's Six Nations tournament
Captain Lewis Moody is likely to miss England's first three Six Nations matches after Bath ruled him out for up to six weeks with a knee injury.
Moody limped off in their Heineken Cup win over Aironi, although he initially thought the knock was not too serious.
England face Wales in Cardiff on 4 February before home games with Italy (12 February) and France (26 February).
They are already without lock Courtney Lawes and flanker Tom Croft for most, if not all, of the tournament.
Moody's absence leaves manager Martin Johnson looking for a new captain, with experienced centre Mike Tindall and
number eight Nick Easter
the most likely candidates to take over.
It's always disappointing to lose a player and leader of Lewis' calibre. But good teams adapt to injuries and that is what we intend to do
England manager Martin Johnson
Bath confirmed on Tuesday -
three days after Moody twisted his knee
- that he had suffered an injury to the medial collateral ligament.
"Lewis took a knock to his knee at the weekend, which is slightly more serious than first thought," said head coach Steve Meehan.
"It is frustrating for us to lose him at this stage in the season, but it does mean that other players in the squad get the opportunity to come on in his place and show us what they can do.
"We will of course make sure he receives the best medical attention to get him back on the field as and when he's ready."
Sixty-six cap Moody will definitely miss England's first two matches against Wales and Italy, and is unlikely to be ready for the game against France.
England manager Martin Johnson said: "It is always disappointing to lose a player and leader of Lewis' calibre.
"But, as I have consistently said, good teams adapt to injuries and that is what we intend to do. While this could still mean Lewis plays a role in the Six Nations, it does mean that another player gets the chance to step up and make it hard for him to get the shirt back."
A new captain will be named in the week leading up to the team's first Six Nations match against Wales.
Easter led England for the first time in a Test against Samoa last November and has also led them twice in non-cap matches against the Barbarians, first in 2008 and again at Twickenham last May before the summer tour to Australia.
The Harlequins forward would relish resuming the role should Johnson turn to him.
"Captaining England is a massive honour and I have enjoyed doing it in the past, so of course, if the opportunity came along, I would take it with both hands," he said.
Moody has been England's regular captain since the final game of last year's Six Nations against France, when he
took over from Steve Borthwick.
elite squad Johnson announced last week,
Hendrie Fourie of Leeds is the only other recognised open-side flanker.
But Joe Worsley has also been used there before, most notably in Cardiff two years ago when he performed a
successful defensive job on Wales centre Jamie Roberts.
Northampton's Tom Wood and Steffon Armitage of London Irish are possible candidates for promotion from the Saxons squad with Johnson already mulling temporary replacements for Lawes and Croft.