The Serbia centre-half has been sidelined since the opening weekend of the season with a calf problem.
He was, however, able to make a return to competitive action on Tuesday when handed an international run-out by his country.
Vidic is now in contention to earn a recall to United's starting XI when they go to Anfield on Saturday.
Ferguson insists there is no guarantee that his club captain will be included against the Reds, with Jonny Evans having shone in his absence, but he has welcomed the selection headache.
"The big question mark is whether Vidic is ready," he said.
"He has his first game for Serbia on Tuesday. It's certainly a consideration because he's such a great competitor.
"He came in yesterday (Thursday) and felt OK. But the Liverpool game is such an intense, stamina-draining game that you want everyone to be 100 per cent so it might be more down to how he feels himself.
"Jonny Evans' form has been absolutely brilliant so I don't have any real concerns about who I play because they're all playing particularly well."