PITTSBURGH — It is impossible to understate the amount of respect everyone in the hockey community has for Dan Girardi, who has given his body and soul to the Rangers since joining the club during the 2006-07 All-Star break, just as it is impossible to overlook his importance in the franchise’s rise to prominence over the last decade.

But it also is impossible to ignore how dramatically the alternate captain’s game has slipped throughout this season in which a rather gradual decline evolved into a steep drop like you’d find riding the Coney Island Cyclone.

Indeed, it was a year of intermittent and extended valleys that was painful to watch, and it continued with a subpar performance in the Blueshirts’ 5-2 Game 1 loss of the first round here on Wednesday against the Penguins that, truthfully, would have left Alain Vigneault with little choice other than to scratch the decorated 31-year-old veteran for Saturday’s Game 2, regardless of how sticky a decision that would have been for the coach.

As sticky as it was for Pat Burns to scratch a healthy Ken Daneyko from Game 4 of the Devils-Boston first round in 2003 after the nearly 39-year-old defenseman had played in every one of the previous 165 playoff matches in franchise history that, by the way, included two Cups that would become three when New Jersey — with No. 3 in the lineup — prevailed in Game 7 of the final against Anaheim later that spring.

Now, though, and serendipitously, Girardi will be spared the ignominy of being cited as a healthy scratch in the wake of either sustaining an injury or aggravating an old one in Game 1. He will miss his first playoff game after playing in all of his team’s 109 since 2007 with an ailment that Vigneault couldn’t or wouldn’t quite describe.

For when asked whether it was an upper- or lower-body injury, the coach swept his hand from his head to his waist and responded, “It’s the whole thing.”

Well, yes, unfortunately it has been for Girardi, who has played the fourth-most minutes in the NHL (playoffs and regular season combined) since the start of 2011-12 — his 10,427 entering the tournament exceeded by Drew Doughty, Ryan Suter and Duncan Keith — and who has played every one of them as if his and the Rangers’ lives depended on it.

So if the Rangers are playing semantics here in order to grant Girardi — who did miss the final two games of the regular season with an upper-body injury — an honorable discharge from the lineup, it is certainly understandable.

Much less understandable, however, was Vigneault’s reluctance to definitely declare that Dylan McIlrath would replace Girardi, even if the coach sort of said that he would by obliquely referring to No. 6 as one of the six healthy defensemen on the playoff roster who had practiced on Friday.

It made no sense, this tap-dance from Vigneault that included the sentence, “If we need him to play, I’m sure he will play well.”

What?

But then, Vigneault’s sparing use of McIlrath throughout the season has made no sense, unless the coach who favors a skating game simply does not believe there is value to having a physical presence on the back line — or does not believe that this rookie is up to speed.

His teammates sure seem to believe that McIlrath brings an important ingredient into the mix. Keith Yandle, with whom McIlrath will be paired (presuming he plays) while Marc Staal and Kevin Klein hook up and Brady Skjei remains with Dan Boyle, said that the freshman “brings a certain aspect to the game that you need.

“He’s a big body who plays a physical game and opens up the ice for me,” said No. 93, who shares a ride to the practice rink every day with McIlrath. “He puts some fear into the opposition.”

That fear factor could come in handy against the Penguins, who raced through the neutral zone without a care in the world and crashed the net with impunity in Game 1. When McIlrath played here on March 3, he stepped up and clobbered Tom Kuhnhackl just outside the line. Pittsburgh won the game, but players on both teams noticed.

“I think you always get a little energy when he lands some of those thunderous checks,” said Chris Kreider, from whom the Blueshirts need more oomph going forward. “So I don’t think it’s a bad thing.”

Bad things have happened all year to Girardi and they have happened to the Rangers when he has been on the ice. The four years at $5.5 million per remaining on his contract — which includes a no-move clause through next season — is going to become an issue once the playoffs conclude.

Now, though, the only relevant issue is performance. It is not about reputation. It is not about credit for past duty that went above and beyond. It is not about sentimentality. It can’t be.

It is about the fact that at the moment, the Rangers are better off with McIlrath in the lineup than Girardi.