Coach Sean McVay said Kupp (knee) won't play Sunday against the 49ers, Myles Simmons of the Rams' official site reports.
McVay hinted at a possible absence for Kupp earlier in the week and provided more definitive word Wednesday. With Kupp sidelined for at least one game, Josh Reynolds will join Brandin Cooks and Robert Woods in the three-wideout formations that comprise the vast majority of the Los Angeles offense. Given that he's recovering from an MCL sprain, Kupp is in danger of missing time beyond Week 7.