Rees linked up with the England squad at their Bath University base on Wednesday, after Moody missed training.
England head coach Brian Ashton will not decide until tomorrow on whether Iain Balshaw will start at full-back.
Balshaw suffered a groin injury during training on Wednesday, meaning his Gloucester colleague Olly Morgan was called up as a precaution.
If Balshaw misses out then Ashton could either draft uncapped Morgan straight into the team or move either Josh Lewsey or Jason Robinson from one of the wing positions.
England will launch their Six Nations campaign a much-changed side, with only two players - flanker Joe Worsley and number eight Martin Corry - retained in their starting positions from the world champions' last fixture against South Africa a little more than two months ago.