Tennessee and Chicago Running Back Situations

Jordan Howard and DeMarco Murray were both held to nine carries in week two due to injuries, and they combined for less than five points. Their backups (Tarik Cohen and Derrick Henry) have outscored them through two weeks, and are now priced equally with Howard and Murray.  Depending on the severity of both injuries, there could either be great value here, or a true time share. How will you approach these backfields in week three?  Does your opinion change for cash games vs GPP's?