It's not a secret: The Rangers played better hockey leading up to the All-Star Break. They won games, and even better, they more or less deserved to win the games they won. Since December 1st, they're firmly middling in Score-Adjusted Corsi: 49.8%, 17th, tied with St. Louis, and within .2 of the Washington Capitals. It's not the best place to be, but it's an improvement from the first part of the season, when the Rangers played terrible hockey and their possession stats showed it.
Tanner Glass, who played two games with the Rangers before December 1st, was left off the below graph for reasons of scale thanks to his play. In his two games, he posted a CF% of 34.4 and a negative SCFRel of -25.5%. Fairly, he was put on waivers and sent down to the AHL. Emerson Etem was (sometimes) playing, but he's since been traded to Vancouver, so I chose to omit him, going off the roster posted on the Rangers' website. The following graphs all use 5v5 data from War On Ice and were generated in R.
The rest of the forwards hovered around 45% Corsi through the end of November, with the main difference being scoring chances for. Nash, Brassard, and Zuccarello stand out, but the team's PDO was well above 100, with all but two forwards above 104. Combine that scoring with Henrik Lundqvist saving almost every shot sent his way, and you get a bunch of articles about sustainability, then an inevitable crash. Thankfully, things shifted. The next graph shows the Rangers' forward corps since December 1st.
Many of the forwards have improved tremendously. Since December, the all-American trio of J.T. Miller, Chris Kreider, and Kevin Hayes have averaged around a 55% Corsi For. Oscar Lindberg, though not American, is up there with them. The rest of the top six are positive possession players.
The Rangers needed these improvements and play adjustments to happen. Some were more drastic than others: Miller's leap is having a huge impact, and he's earning his contract come summertime. Kreider's shooting percentage is currently a bit lower than his career average, but he's generating scoring chances; he's a net positive player even if it's frustrating to watch pucks not go in. Zuccarello, Nash, and Brassard aren't having quite the same relative impact as they were at the beginning of the season, but it comes as the rest of the top nine are contributing.
Unfortunately, and as always, downsides exist. Here's the extent to which I expanded the axes to get Daniel Paille on the previous graph:
That's not ideal. He's only played 3 games, as has Megna, but indications are AV plans to keep Paille in the lineup. Maybe he improves, but probably he doesn't. In a perfect world, the Rangers would play a fourth line akin to the one they had in 2013-14, instead of a line used the same way, but unable to keep up. The bottom of the lineup is dragging down the team.
Said ad nauseam, here and elsewhere: Alain Vigneault needs to optimize his roster decisions and TOI allocation to improve the team. This works for the defense and it works for the forwards. Until then, it'll be offset-- there's only so much players like Miller, Hayes, Yandle, and Kreider can do.
Two months isn't a huge sample size. The hope is that this level of play carries forward, instead of a return back.