Petrov suffered lateral knee ligament damage during the first half of the Premier League clash with Sunderland at the Stadium of Light last weekend.
The Bulgaria international will concentrate on rehabilitation work to recover from the setback, but Villa manager Gerard Houllier is resigned to being without the 31-year-old until the new year.
The Frenchman confirmed: "We thought Stiliyan would need an operation. He won't need an operation.
"But the time for recovery will still be the same - between eight and 12 weeks."
Houllier has received mixed injury news regarding his full-backs ahead of Sunday's derby clash with Birmingham.
Luke Young has recovered from a hamstring problem which has sidelined him for the past three matches and has been included in the squad, but Habib Beye, who has replaced the former England defender, is rated doubtful with an ankle injury.
Source: Team Talk