Interim England captain Mike Tindall will see an ankle specialist before any decision is made over his possible involvement in Saturday's clash with Ireland.
Tindall, who has led England to the brink of a first Grand Slam in eight years in the absence of Lewis Moody, was forced off at half-time of the 22-16 victory over Scotland.
The Gloucester centre left Twickenham in a protective boot - and although he has not fractured the ankle, he will now see a specialist over the results of a MRI scan.
"Of course losing Mike would be a blow, and especially so for Mike himself after what he has done for the team, but leadership is one part of our game that has really developed over the last 12 months," said England manager Martin Johnson.
"If Mike is not fit to go, then the guys will just crack on.
"Matt did really well in that position when he came on, while the leadership within the group has been sound."
Banahan in the clear
Matt Banahan is the most likely replacement for Tindall if he is ruled out - the 6ft 7in Bath back having avoided disciplinary action for a clash with Kelly Brown, while Nick Easter is the favourite to take over the captaincy.
Scotland lock Brown was stretchered off at Twickenham after tackling Banahan, who always denied he had led with his forearm - a view shared by the official citing officer who ruled there was no case to answer.