2 years ago the Rangers were a good puck possession team up until the playoffs, where they got beat by a much better puck possession team in the Kings. Last year they were much poorer at possessing the puck, but were well supported by top 4 ES shooting % and top 5 ES save %. The linked graph shows the Rangers' puck possession numbers for the last 2 seasons: Graph
I think you're seeing the Rangers come crashing down to earth right now. Their puck possession numbers are the worst they've been in the last 3 years. Obviously Lundqvist isn't this bad, but he's also not as good as his numbers suggested at the beginning of the year. It's highly unlikely that Lundqvist returns to putting up the numbers he was at the beginning of the year (because no goalie can), so there's not much to suggest the Rangers return to being a team at the top of the conference. Plus, the Rangers have the 2nd highest ES shooting % this year at 9.4%, which is tough to sustain. That could help explain their good start despite poor puck possession numbers, yet also give them room to fall.