England face the prospect of entering their clash against Scotland without Owen Farrell after concerns over his fitness escalated on the eve of the Twickenham showdown.
Farrell was unable to take part in the captain's run on Friday due to the unspecified leg injury sustained in training 24 hours earlier and he now faces a race against time to prove he can take part.
"Owen didn't train today (Friday) and we're monitoring his leg injury. It's a leg injury," defence coach Paul Gustard said.
"We have until tomorrow before kick-off to make a decision, which means he has at least another 24 hours of recovery ahead of him."
England have opted against calling in another player. The most probable contingency if Farrell is forced to withdraw would see Ben Te'o promoted from the bench to fill the void and Jonny May, who is currently acting as 24th man, stepping on to the interchange bench.