Goals against under Renney:
2005-2006 4th
2006-2007 9th
2007-2008 4th
2008-2009 year he was fired 6th, yeah I'm not buying the whole defense was trash argument. No doubt Henrik was great those years but he was protected a lot better in Renney's system than he is now playing behind a much better defense corps. This team can't handle man to man, they just can't. Lundqvist looks human this year because the defense is different, more holes, more chances.
Man on Man D is used by only a number of teams in the NHL. As a system for 200 x 85 rink, it leaves a lot of gaps to be exploited if the defender is a step behind, either cause of speed, position, or read. That's why if one man loses or gets exploited on his man on man assignment, then a scoring chance results, or there is a zone pressure because of successive break downs or the team in recovery mode.
EDM uses it, DET uses it, TB uses it. It's built more more for slick skating teams that can defend with the stick and get takeaways. Unfortunately this means when the team has the puck the goalie better be good at handling the puck and not letting teams establish a forecheck to begin with.
Plus you need very smart, very good skating defensemen that can really make good reads and move the puck. This is why you see McD and Stralman shine under this system.
G looks bad or exploited from time to time because he's getting caught on neutral zone turn overs when the Rangers zone entry fails. DZ looks bad because his reads are slow. John Moore gets mesmerized by his assignment and doesn't read his teammates so there's poor gap control. Staal's never been a good puck handler so he's getting caught trying to move the puck faster than his hands allow him to.
These are caveats to Man on Man D that's lead to this record and a lack of defensive structure or identity. Better part of the last decade other teams knew they were going to have a tough time scoring against the Rangers. Unfortunately for the Rangers, they have a tough time scoring against other teams.
Man on Man D changes part of that, adding in higher elements of risk; and when that risk is taken and not rewarded, it's almost always a high quality scoring chance going the other way.