Sir Alex Ferguson expects Jonny Evans to be out of action for a fortnight after he was forced out of Manchester United's 5-0 win over Wigan with a calf injury at Old Trafford on Boxing Day.
Evans was United's only fit central defender heading into the game and failed to reappear for the second half as Dimitar Berbatov bagged a hat-trick.
And Ferguson confirmed the Northern Ireland defender will not make the New Year's Eve encounter with Blackburn.
"Jonny came off injured. He has a calf injury and will be out for two weeks," Ferguson told BBC Radio Five Live.
"We have had a nightmare the last few days. Phil Jones and Chris Smalling have both been ill. Rio Ferdinand called off yesterday with a back injury and Jonny Evans has come off at half-time.
"It does put you under pressure."
Ferguson is hoping Jones and Smalling will have recovered from their problems before the Blackburn game, although with a trip to Newcastle to follow and then the blockbuster FA Cup third round tie with Manchester City at the Etihad Stadium on January 8, it is the wrong time to be affected by an area of the pitch from which skipper Nemanja Vidic will be missing for the rest of the season.
It is the one cloud on a very healthy festive period for United so far.
The Red Devils' second successive five-goal win allowed them to move level on points with neighbours Manchester City, and slice the Blues' goal difference advantage in half.