49ers' Elijah Mitchell: Leaves with knee injury Sunday

Mitchell won't return to Sunday's game at Chicago due to a knee injury, Matt Maiocco of NBC Sports Bay Area reports.

Mitchell may have been the victim of terrible field conditions on a soggy Soldier Field, but the second-year pro will finish Week 1 with six carries for 41 yards. With rookie third-round pick Tyrion Davis-Price a healthy scratch Sunday, the 49ers' healthy options at running back are Jeff Wilson and Jordan Mason.