The Facts: McKinnon will undergo a platelet rich plasma injection and will miss two weeks, HC Kyle Shanahan said.

Diehards Line: McKinnon missed practice Thursday after experiencing knee soreness, Shanahan said, via Nick Wagoner of ESPN. The running back participated the previous two days after the 49ers removed him from the physically unable to perform list. Wagoner added the 49ers hope he can return in time for the season opener. Fortunately for San Francisco, it is well stocked at the position with Tevin Coleman and Matt Breida as its top-two backs.