Samuel (hamstring) didn't participate in the early portion of Friday's practice, Nick Wagoner of ESPN.com reports.
With Samuel absent from the initial stage of practice Friday after sitting out Wednesday and Thursday's sessions, he's trending toward an absence Sunday against the Raiders, as is fellow WR Mike Evans (Achilles). Confirmation of the duo's status is set to arrive later Friday once the 49ers' final Week 9 injury report is posted.