According to Scott Blair of NBC, "Doug Martin has an injured knee. (Coach John) Gruden says his status is uncertain for Sunday. (The) Raiders needed another runner, which is why they signed C.J. Anderson."
If Martin sits, Jalen Richard is the guy to target in Oakland. Anderson likely won't have time to get up to speed enough to see more than a few touches, potentially thrusting Richard into a three-down role. That sort of usage would put him on the RB2 radar.