49ers' Christian McCaffrey: Headed to IR, out at least six weeks

The 49ers plan to place McCaffrey (knee) on injured reserve, Ian Rapoport of NFL Network reports.

Coach Kyle Shanahan announced Monday that McCaffrey suffered a PCL injury in his knee, and he will be sidelined at least six weeks, Rapoport added. CMC was injured in the first half of Sunday night's eventual loss to the Bills, and he's now going to miss at least the rest of the regular season. In addition, McCaffrey's backup, Jordan Mason, suffered a high-ankle sprain against Buffalo and was also placed on injured reserve Monday, knocking him out until at least Week 18. It vaults Isaac Guerendo into the 49ers' RB1 spot atop the depth chart, making him a priority add in all fantasy leagues. Patrick Taylor is currently on the team's practice squad but will likely be promoted this week.