Evans expected to miss two weeks
Evans was United's only fit central defender heading into the Wigan game, but the Northern Ireland international failed to reappear for the second half.
And Ferguson revealed after the match that Evans will not make the New Year's Eve encounter with Blackburn Rovers. "Jonny came off injured. He has a calf injury and will be out for two weeks," he 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."
With United now level on points with Premier League leaders Manchester City, Ferguson can ill afford to be without another defender for long.
However, the Scot, who is already without Serbia centre-back Nemanja Vidic for the rest of the season, hopes Jones and Smalling will have recovered from their injury problems before the Blackburn game