While they welcomed quarterback Jimmy Garoppolo back from his right thumb injury, the Niners' pregame inactive list included a trio of key players: star left tackle Trent Williams, nickel cornerback K'Waun Williams and linebacker Marcell Harris.
All week, signs pointed to Garoppolo being available after he practiced on a limited basis and made it clear that the only issue with his thumb was pain management. Garoppolo started against the Rams, though rookie Trey Lance also took reps with the starting offense during the week.
"He had a good week," coach Kyle Shanahan said of Garoppolo on Friday. "Yeah, a good week of practice when he was in there. I feel good with where he is at right now."
Garoppolo had been listed as questionable on the injury report with a handful of other 49ers. Often this season, players with that designation have been available, but that wasn't the case 90 minutes before Sunday's game.
The absence of Trent Williams wasn't necessarily a surprise, since he didn't practice all week, but Shanahan said Wednesday that he expected Williams to be available. That stance seemed to soften as the week went on, as Shanahan said Friday that "hopefully" Williams would play.
"You always want the best tackle in the league out there, so you don't feel as good if he can't go out there," Shanahan said. "But Jaylon Moore's got some opportunities this year, he's played some good football. And we also have Colton McKivitz, who hasn't got a chance this year, but last year he got a start at guard versus the Rams, so he'd be an option also."
The Niners also were missing K'Waun Williams, their primary nickel cornerback, who was cleared from the reserve/COVID-19 list on Saturday and had no injury designation. It's unclear why Williams was a pregame scratch before the Niners attempted to slow down Rams wideout Cooper Kupp.
Harris (Achilles), defensive tackle Maurice Hurst (calf), linebacker Azeez Al-Shaair (knee) and defensive back Jarrod Wilson were also inactive. Hurst, Harris, Al-Shaair and Trent Williams were all listed as questionable on Friday's injury report.