Whether or not Jamaal Charles is out for an extended period of time or not, Knile Davis showed more than enough talent to warrant a spot on your team. Sure, if Charles is out, he becomes a sure-fire RB2 with loads of PPR upside (peep those nine targets!), but if he's not, you can still likely enjoy 10 touches per game from one of the most talented handcuffs in the league, especially given the support that noodle-armed Alex Smith needs in the passing game from his backfield.
It's also worth noting that while Davis' (and the Chiefs') schedule in the recent weeks isn't fantastic, come fantasy playoff time, it's softer than Chicago's run defense. You've got the Raiders twice, an injury-depleted Cardinals, and the rematch with the Broncos at home.