Mostert (knee) has been ruled out for Sunday's game against the Eagles, Cam Inman of The San Jose Mercury News reports.
With Mostert out another week and Tevin Coleman (knee) on injured reserve, Jerick McKinnon is set to lead the San Francisco backfield again. Jeff Wilson and JaMycal Hasty will provide depth, while Mostert will hope to make it back for Week 5 against the Dolphins.