Jefferson (knee) didn't practice Friday and won't play in Sunday's game against the Cardinals, Josh Weinfuss of ESPN.com reports.
The third-year pro still hasn't practiced since having minor knee surgery in early August, but his role as the No. 3 receiver appears fairly safe given the lack of production behind Cooper Kupp so far. Ben Skowronek, filling in as the No. 3, has managed only six catches for 41 yards on nine targets in two games, playing 88 and 86 percent of snaps on offense. Jefferson should be more of a threat if/when he moves past the knee surgery and reclaims his role. The lack of practice reps suggests that's unlikely to happen for Week 4 at San Francisco, though the Rams haven't officially ruled him out beyond Week 3.