NEW YORK — It becomes inevitable at some point for any team like the New York Rangers that the window to win a Stanley Cup championship eventually begins to close. It would be hard to think of a day where it’s felt more like it’s been completely slammed shut than the one the Blueshirts went through on Monday. A 5-2 loss to the St. Louis Blues — who were enjoying the boost of having hired a new head coach, Jim Montgomery, who made his debut for the team in this game — made it three straight defeats for the Original Six franchise, whose current on-ice group seems to have been exposed as having some challenges in defending. For the third straight game, they allowed 40-plus shots, and have been outscored 14-6 over that stretch. Usually, there’s at least something good to take away, some form of a positive to build off of heading to the next game. “I don’t know if there’s anything good you can find from tonight,” said Rangers superstar forward Artemi Panarin. It isn’t necessarily that it isn’t good enough within the context of the National Hockey League as a whole — the Rangers are the Eastern Conference’s fifth-best team with a 12-7-1 record and 25 points on the season — but, moreso, with the standard they’ve set over the past few seasons. In the same way some fans called for the job of Yankees manager Aaron Boone after he lost to the World Series, the expectation one borough over is to win. The same can be said for the Rangers, who lost in the Eastern Conference Final last year to the eventual champion Florida Panthers, but seemed to be on a trajectory towards getting back to the Cup Final for the first time since 2014. So, yes, while many fanbases would be thrilled with being in a playoff spot at the moment, it isn’t good enough in Manhattan. Not to the fans, not to the players, and certainly not to head coach Peter Laviolette, who was fuming after a second consecutive questionable effort and responses from his team after getting down on the scoreboard. “We’re giving up too much, there’s no question,” he said. “We’re not going to win giving up 40-50 shots, we need to be much tighter with what we’re doing and we need more.  There are parts of the game where I thought we were good, there’s parts of the game where we weren’t very good at all. We gave up a goal to start the third period, and I didn’t like the response after that; that’s a time to dig in and go get the next one and bring it back to even, and we weren’t able to do that.” Certainly not helping matters was a report from Canadian-outlet Sportsnet earlier in the day that Rangers general manager Chris Drury had dangled stalwart forward Chris Kreider and team captain Jacob Trouba to the rest of the league via trade. A message seemed to be sent with the call-up of Brett Berard and Matt Rempe from AHL Hartford to replace Kreider, who was day-to-day with an upper body injury according to the team, and Jonny Brodzinski to try to spark the team. Berard, a speedy forward out of Providence College, did tally a secondary assist in his NHL debut, but ultimately neither he nor Rempe were able to make much of an impact in this latest Rangers tailspin. “I had butterflies for the last 24 hours, and it was pretty awesome and a dream come true,” Berard said of his debut. “You only have your first game once, so it’s pretty cool to have and take it all in. It’s definitely a relief to have it, and just continue to build off tonight.”