Do we really want Ledley to stay another year as a player? He's past it now, unfortunately. Give him a coaching role. There's no point having him on the books and dragging him out everytime he thinks he's fit enough to play; it's unsettling for the defence and it's not reliable backup. I'd be happy with a back 4 of Caulker, Vertonghen, Dawson, Kaboul + a youngster / older defender, who'd be happy to play a bit part. I know Ledley would be content to be backup, all things considering, but like I said, he's just not reliable to stay fit should he have to be called upon in emergency.
