Lenoir (shoulder) has been ruled out ahead of Sunday's matchup against the Cardinals, Bo Brack of GoPHNX.com reports.
Lenoir appears to have sustained a shoulder injury in the 49ers' Week 17 loss to the Lions, despite playing 100 percent of the team's defensive snaps and recording nine total tackles. The Oregon product was unable to practice all week due to this issue, making it no surprise he won't suit up in Week 18. With Lenoir sidelined Sunday, Rock Ya-Sin or Isaac Yiadom (pelvis, questionable) will likely serve as one of San Francisco's starting cornerbacks.