The Serbia international has not played competitively since August since suffering a calf injury.
"The big question mark is whether Vidic is ready," said Ferguson. "It's certainly a consideration because he's such a great competitor.
"He came in yesterday (Thursday) and felt okay, but the Liverpool game is such an intense, stamina-draining game that you want everyone to be 100% so it might be more down to how he feels himself."
Vidic will discover whether he has made the starting lineup when United travel to Anfield on Saturday.