Hayes suffered a knee injury last week against Dallas and left the locker room on crutches with his knee wrapped. Although Hayes isn't technically a starter, he's one of the Rams' most valuable and versatile defenders.
Not having Hayes available is never a good thing for the Rams but it could be particularly damaging this week.
Hayes is the team's best run defender among the defensive ends and played a pair of strong games against San Francisco last season. His knack for setting the edge against the run as well as breaking through and stuffing it himself will be sorely missed against a team the Rams are expecting to return to its running roots this week.
In the two meetings between the teams last season, Hayes had five tackles 1.5 sacks, a tackle for loss and a quarterback pressure.
Taking Hayes out of the mix puts the onus on Chris Long, Robert Quinn and Eugene Sims to handle the bulk of the work at end. It also probably means rookie end Gerald Rivers will be active for the first time in his young career. Sims has proved a solid run stopper in the past and the Rams will need him to be on top of his game to help replace Hayes' production.
Elsewhere on the injury report, the Rams also ruled out right tackle Rodger Saffold, who has a knee injury of his own. Like Hayes, Saffold also didn't participate in practice this week.
Here's the full rundown on the injury report:
Out: Hayes, Saffold