I want to feel bad for the dude, because he's clearly a NHL calibre defender, but he's been given tons of chances to move off of the 3rd pairing and has been passed by basically everyone in the system and forced our hand in trade/free agency a few times now.
When he broke in, our depth chart looked like this:
LD: Rielly, Gardiner, Rosen, Borgman, Marincin
RD: Hainsey, Zaitsev, Carrick, Polak
We've spun a bunch of stuff through our blueline between then and now...Ceci, Barrie, Holl, Muzzin, Brodie, Bogo, Lilly, Sandin.
and despite the turnover of the next 2 seasons, he was never able to establish himself as more than the 3rd pairing LHD, which is one of the most replaceable lineup slots in hockey. It is not difficult to find a Left handed defender who doesn't get caved in sweet heart matchups. He's gotten beaten out for minutes and opportunity by pretty much every functioning NHL'er we've had come through. There might be more upside in there, but I don't think we're going to see it in Toronto regardless of how long we wait. He needs a shit team that is going to over play him and hand him an opportunity above his current level of play and hope that he grows into it. The tools are there, but he's not going to get there on merit.