Samuel (hamstring) did not participate in the portion of Thursday's practice open to the media, Nick Wagoner of ESPN.com reports.
Samuel hasn't played or practiced since sustaining a hamstring injury in San Francisco's Week 5 win over the Seahawks. He'll likely require at least some ramp-up period upon returning to practice, and GM John Lynch indicated Thursday that Samuel is expected to sit out Sunday's game against the Raiders. Samuel's likely to be formally ruled out on Friday's injury report.