I think he's solid, but not good enough to steal games. The back end is weak, especially if Ericson cannot play. My hope is the speed of the young guys keep Boston playing in their end more. Chara is very overrated IMO. That guy has no speed at all. He's very solid when the play is prolonged in the zone, but in open ice he is exposed by quicker players.
Someone is not a fan of advanced metrics I see... Chara faced the strongest competition of any elite D and yet still drove play in the other direction at all times. He and Bergeron are the prime reason that Boston is the possession monster that they are, as both have ridiculous Corsi numbers despite starting predominantly in the defensive zone. Going by advanced metrics they should both be locks for the Norris and Selke, though Chara didn't put up enough assists to get it (cause clearly more assists indicates superior defensive play!)
The metrics may favor him, but every game I have seen of his in the last two years he gets schooled in open ice. He just excels at 'half court' defense IMO. Just because he has great numbers doesn't mean he can't be exposed. Nyquist did that earlier this year. It's like watching a LT try to get out wide on a blitzing corner.
