If you're a Jamaal Charles owner, Knile Davis is essentially a must-add handcuff, especially with Charles nursing a sore knee.
But even if Charles is floating off on someone else's roster, it might be worth it to speculate on Davis, just on the chance that the Chiefs are downplaying Charles' injury and he doesn't play. The Chiefs' offense is tailored to the run (and to short passes to the running back), and Davis will slide into the Charles role if anything happens.
Additionally, a team hurting at running back with byes and random injuries might even be able to flex Davis, under the logic that Charles could be limited in Week 9.
If you're carrying a backup tight end to Jimmy Graham, or have a quarterback you'll never start, it might be worth it to bail on them and speculate on Davis.