Ferguson admitted he may leave it up to Vidic himself to decide whether he is fit enough to make his first start for his club in two months.
"The big question mark is whether Vidic is ready for the game," said Ferguson.
"He had his first game [back] for Serbia on Tuesday, played the full game, so he is certainly a consideration because he is such a good competitor.
"Nemanja came in yesterday and felt okay, but a Liverpool game is such an intense, draining affair, you want everybody to be 100 per cent.
"It may be down to how he feels himself, we'll have to see.
"All the players have come back from the internationals fit, which is always a blessing. Sometimes they don't, but fortunately this time they are all okay."