The thing is, even though we all agree Hagelin is having a down year - he is still producing at a 1st line level 5v5 without having played on the 1st line all year.
Carl Hagelin has put up
1.92 5v5 P/60 which is 71st among forwards (3rd on the Rangers behind Nash and Zuccarello), which is right in line with his career average. His decrease in absolute numbers has come from reduced TOI/G.
Other players producing at a similar rate to Hagelin: Claude Giroux (1.95, 69th), Paul Statsny (1.96, 68th), Jason Pominville (1.90, 79th), Henrik Sedin (1.89, 83rd), Eric Staal (1.88, 85th), Jaromir Jagr (1.87, 87th), David Krejci (1.84, 96th), Patrice Bergeron (1.82, 100th), Alex Ovechkin (1.81, 101st).
Hagelin is at worst a good top-6 winger 5v5, and I'd even go so far as calling him a legit 1st liner
in that situation. And considering that we have depth players that can play on the PP like Brassard, his inability to translate his skill to the PP doesn't hurt us.
Let's remember, Nash has played
by far his best hockey as a Ranger with Hagelin on the opposite wing.