49ers RB Jerick McKinnon to undergo MRI on injured knee
McKinnon injured himself in practice on Sunday and the team says he will be re-evaluated in a week.
McKinnon signed a $30 million, four-year contract in March. He lost four yards on three carries during his preseason debut, when he played one possession against Dallas on Thursday.
The 49ers already are without backup running back Matt Breida, who is out until the start of the regular season with a shoulder injury. Joe Williams also missed practice because of a death in the family.