So this is what the NHL has as a matter of entertainment, after at least three times within a week codifying as legal checks, on which the attacking player finishes off his opponent with a forearm or elbow that drives his prey into the glass or boards.

The NHL has a quagmire like last night’s aesthetically displeasing match at the Garden, in which the Canadiens registered a 3-1 victory over a Rangers team that was comatose without Rick Nash, sidelined with what are believed the after-effects of taking such a blow from Milan Lucic in Boston a week ago last night.

The Rangers aren’t saying anything about the condition of Nash, who played two days after taking the unpenalized hit and then again three days after that despite a couple of days that we know of, when he wasn’t feeling well. No one is saying whether No. 61 is suffering post-concussion symptoms. Perhaps more to the point, no one is saying he isn’t.

A blow to the head cleverly and maliciously disguised as finishing a check, and a wink and nod from the league. On Saturday night, the Flyers’ Braden Schenn concussed Canadiens rookie Brendan Gallagher on a similar check that went unpenalized. Monday night, Montreal defenseman P.K. Subban took a circle route to deliver the same kind of blow against the Hurricanes’ Alexander Semin.

It’s impossible to know how many more of these checks have been thrown, but three within a week connotes a trend. If this becomes commonplace, if this permeates the game with the blessing of the NHL, then the Department of Player Safety will become an oxymoron.

The absence of Nash from the lineup — the length of which at this point is both undetermined and indefinite — does not excuse the Rangers’ sloth. Neither is it excused by the style employed by the Canadiens, who put on a display of neutral zone- and middle-packing that made Jacques Lemaire’s most stringent trapping teams look like the Oilers of the early ’80s.

One game shy of a third of the season, the Rangers haven’t been able to gain any traction. They are 8-6-1 after having played 10 of their first 15 at the Garden, and even though last night’s defeat was their first in regulation in their last six matches (4-1-1), their play hasn’t inspired confidence.

There’s a step forward, a step back. They’ve surrendered leads. They’ve been impotent on the power play. They have not generated a consistent forecheck. There is no cause to leap off a building, but there’s no call for anyone to place an order for confetti, either.

What a downer last night. The Canadiens, who have surrendered a total of two goals over the last four games of what is now a five-game winning streak, played the night before in Montreal. Yet the Rangers seemed as tired as their opponents, unable to ever press the issue, unable to pin the Canadiens on their heels, unable to press the issue against Carey Price.

And this coming directly after what was likely the Blueshirts’ best effort of the year, Sunday’s 2-1 victory over the Caps that featured pace, grit, attention to detail and determination.

That was a throwback game. Last night was a throw-up game.

“It’s very disappointing to follow that with this, especially in this shortened season,” Ryan Callahan told The Post. “You want to build energy and confidence off of a game like that, but for whatever reason we didn’t.

“We need to do that, especially in a 48-game season.”

The Rangers need to be better; much better. Other than Carl Hagelin and perhaps Marc Staal, there isn’t a single Ranger playing as well as he did last season.

This can’t be about the absence of Nash, short-term or long-term. If it is, 2012-13 is about to become a huge headache.