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.