Samuel (hamstring) has been ruled out for Sunday's game against the Raiders, Nick Wagoner of ESPN.com reports.
Neither Samuel nor Mike Evans (Achilles) made a serious bid to play in San Francisco's first game after a Week 8 bye. Jordan Watkins, Brandin Cooks and Jacob Cowing are the healthy WRs on the active roster, with Demarcus Robinson (ankle) a candidate to come off injured reserve this week or next.