Sadly he hasn't met his potential, which he had bags of.
Lovely on the ball but for me, a CB should be a dominant presence, which he just isn't. He's basically too nice.
I lost interest in that period earlier this season when he turned up for a game with a black eye looking like he'd spent 3 months living rough hammering the Spice.
There are better CBs out there, so for me, he can be replaced.