LONDON (Reuters) -- Aston Villa captain Stilian Petrov will be out for at least two months after the midfielder injured his knee in Saturday's Premier League defeat at Sunderland.

"Unfortunately I think we have lost Stilian Petrov for maybe at least two months," Villa manager Gerard Houllier told the club's website ( on Monday.

"We will see if he needs an operation or not -- we will know that by the middle of the week."

The Bulgarian international picked up the injury in the first half of Saturday's 1-0 defeat, which left Villa in 10th place after nine matches.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.