Well, that stems from the fact he's still learning and shouldn't be starting for a top four side. Think he could still be a very good CB option as exemplified by his imperious performance against Spurs in the CC.
As with James, I really feel the more pressing defensive concerns lie with our midfield.
Regarding Djourou, I can definitely see where you're coming from Gurgen. Not sure myself, he may not be positionally perfect but he anticipates things fairly well I'd say.