Rio Ferdinand could miss tomorrow's Carling Cup semi-final against Manchester City after being hit with a violent conduct charge by the Football Association.
The charge relates to an incident with Craig Fagan during the second-half of Manchester United's 4-0 win over Hull at Old Trafford on Saturday when Ferdinand appeared to deliberately strike the Tigers striker in the face with his arm.
After some initial confusion, the FA have now confirmed that if Ferdinand admits guilt by 6pm tomorrow night, the first game of an automatic three-match ban will be the City encounter, when a place at Wembley is at stake.
Ferdinand does have the option of appealing and having the case set before a disciplinary hearing on Thursday.
However, if the panel decides United have deliberately taken that option to allow their 31-year-old centre-half to play tomorrow, it is possible they may add an additional punishment if guilt is established.
Either way, Ferdinand could miss Sunday's Premier League trip to Arsenal, plus the home encounter with Portsmouth on February 6.
If Ferdinand plays against City the third match of any suspension would be at Aston Villa on February 10.
Losing Ferdinand would be a bitter blow for Ferguson given the defender has only just returned from three months out with a back injury.
Although Ferguson felt the England defender was not unduly tested against Hull, he accepted Ferdinand's presence had a galvanising effect on his back four, which he was hoping would continue against City tomorrow night.
"Rio's performance level is important," said Ferguson.
"It is important to have him back because getting the centre-halves fit is key to our progress this season."