Thornton (undisclosed) did not participate at the Raiders' training camp practice Tuesday, Ryan McFadden of ESPN.com reports.
Thornton left practice early last week Friday after presumably suffering some type of injury, and he still hasn't been able to make his way back onto the practice field. If he can't play in Thursday's preseason contest versus the Cardinals, it could open up more opportunities for rookie sixth-rounder Malik Benson and offseason free-agent acquisition Dareke Young.