"We thought it was a bad one," United coach Sir Alex Ferguson said. "He's out for the season. It's not unexpected but it's still bad news."
Vidic, 30, was injured in the first half of Wednesday's 2-1 Champions League loss at Basel in Switzerland. He was carried off on a stretcher in the match, which eliminated United, and left St. Jakob Park on crutches.
The retired Serbian international sustained the damage to his right knee, and will require surgery that will sideline him through at least May when the EPL season ends.