Niners HC Kyle Shanahan confirmed Monday that RB Christian McCaffrey will miss at least the rest of the regular season with the PCL injury in his right knee. He also revealed that RB Jordan Mason will head to IR with a high-ankle sprain.

49ers HC Kyle Shanahan said after Sunday night's loss to the Bills that RB Christian McCaffrey has a PCL injury that could be season-ending. McCaffrey will likely undergo additional testing on Monday to get a better look at the damage. We should get another update on his status over the next 24 hours. McCaffrey's absence would leave Jordan Mason as San Francisco's lead back once again. He out-carried RB Isaac Guerendo 13 to four in Buffalo. Mason, who's rostered in only 37% of Sleeper leagues, is the top target on waiver wires this week.

49ers RB Christian McCaffrey exited in the second quarter of Sunday night's game vs. the Bills with an apparent right leg injury. He went down on his own with no contact. We'll update his status when we know more.

Update: McCaffrey is officially questionable to return with a knee injury.

Update: McCaffrey won't return, HC Kyle Shanahan said in an interview before the second half started.