The Rangers have not made an offseason head-coaching hire from within their system since 1973, a half-century ago.

That is when Emile Francis stepped back for the second time from his dual role as GM-coach and hired Larry Popein, who’d been the bench boss of the AHL affiliate Providence Reds.

Popein lasted 41 games, two short of Bernie Geoffrion’s tenure in 1968-69 when he temporarily replaced Francis behind the New York bench.

So it would be a classic Costanza opposite move for the Blueshirts to promote Kris Knoblauch from the AHL Wolf Pack if Gerard Gallant is dismissed, and honestly, at this point what type of message is the hierarchy sending the players through its lack of public support for the coach?

Here’s something else to chew on. One of the reasons David Quinn was dismissed after the 2020-21 season is because of the team’s penchant to get off to slow starts. That was interpreted, accurately or not, as evidence of either a lack of preparation, an inability to motivate, or both.

Following Game 1 against the Devils, the 2023 playoff Rangers scored only one first-period goal the rest of the series, that one scored by Chris Kreider at 19:35 in Game 6.

The first two games of the Devils’ second round in Carolina sure didn’t flatter the Blueshirts, either.

The 44-year-old Knoblauch — who spent six games behind the Rangers’ bench in 2020-21 when Quinn was in COVID protocol then two more the following season when Gallant had tested positive for the virus — drove Hartford to its first playoff spot since 2015 with a 10-1 finishing kick that included an eight-game winning streak before losing the season finale.

And now the Wolf Pack have advanced to the division finals against Hershey after defeating Springfield in a two-game sweep of a best-of-three and a four-game victory over Providence in a best-of-five culminating on Friday with Dylan Garand’s second shutout of the playoffs.

And who is the Pack’s best player? Tim Gettinger, maybe?

Sometimes it is not about the biggest name. Sometimes it is not about marquee value. Sometimes, chicken salad on rye, untoasted, with a cup of tea hits the spot.

If the Rangers underachieved, if the Bruins underachieved, I don’t think the Islanders did. Indeed, in achieving a bottom-rung seed that was followed by a first-round elimination by a superior team, the Islanders probably hit their ceiling.

The roster does not have either the speed or talent to meaningfully compete in this NHL. Grinding for 82 games has its limits. The Islanders reached those limits this year with a roster that included too many forwards two years beyond their respective expiration dates but still with years remaining on contract extensions.

An entire year of Mat Barzal and Bo Horvat could represent seeds of optimism, but only if the former Canucks captain — who was dreadful against Carolina in Round 1 — approaches the level with which he played in Vancouver this year before he was traded. Indeed, this 49-game stint with the Canucks in which the 28-year-old recorded 54 points (31-23) represents the only time he reached a point-per-game in nine seasons in Vancouver.

With no word on major-domo Lou Lamoriello’s status, there is no telling whether Lane Lambert will get a second run behind the bench with a lineup that might be more facile to direct.

When the record-breaking 2018-19 Lightning were bounced in the first round by Columbus, and in no less than a sweep, there was widespread agreement that Tampa Bay had constructed a roster that was too reliant on talent that was not conducive to playoff success.

Hence, the famous 2020 pre-deadline trades for Blake Coleman and Barclay Goodrow that changed the club’s nature in advance of consecutive Stanley Cup championships. There was an obvious flaw in the pre-sandpaper Lightning. And just about every add since then has been in the same vein.

But there is no such identifiable flaw in the record-breaking 2022-23 Bruins roster that had talent so deep that Taylor Hall was on the third line and had grit and gumption that was overflowing even before adding Garnet Hathaway and Tyler Bertuzzi at the deadline.

That is what makes Boston’s first-round exit the most shocking of them all.

Well, except for the B’s 1970-71 first-round, seven-game ouster by the Canadiens and tyro goaltender Ken Dryden.

If you were not there for it, if you’re checking disparities in the standings and see that those Bruins finished just 24 points ahead of Montreal as opposed to this Boston team having outdistanced Florida by 43 points and are influenced by this, you are missing it.

Those Bruins had Bobby Orr at his peak. They had Phil Esposito at his peak. They had Johnny Bucyk, Ken Hodge, Wayne Cashman and Gerry Cheevers at their respective peaks.

They were defending Cup champions and had shattered an NHL record by scoring 399 goals (in 78 games), 108 more than the runner-up Habs and 96 more than the previous standard established by Boston two years earlier.

And then they won the Cup again in 1972.

It does not matter what the numbers tell you. Montreal-Boston in 1971 is the most shocking first-round upset in history.

Two centers, one team, who do you like (after the Oilers’ unassailable Wayne Gretzky-Mark Messier combo): A) Pittsburgh’s Sidney Crosby and Evgeni Malkin; B) Colorado’s Joe Sakic and Peter Forsberg; C) Detroit’s Steve Yzerman and Sergei Fedorov; D) Edmonton’s Connor McDavid and Leon Draisaitl?

I wonder if Marc Staal taught Sam Bennett that net-front crosscheck to the neck/head.

If you had known before the series that Patrick Kane (1-5-6) would outscore Jack Hughes (3-2-5) and Timo Meier (0-0-0) combined, in how many games would you have had the Rangers?

Five?