Dallas Cowboys defensive end Anthony Spencer has revealed that he is doubtful for his side's season opener on Sunday.

The 29-year-old suffered a setback in his recovery from knee surgery during practice this week and is not confident about facing the New York Giants this weekend.

"I mean there is a possibility," Spencer told Dallas Morning News.

"But I really haven't done too much this week so I don't feel very confident. We'll see."

Spencer had a career year in the 2012 season as he registered 11 sacks, the highest total accumulated in his six years in the NFL.