We are conditioned to believe that a dark cloud sits permanently over Penn Plaza, even on the sunniest of summer days. Two decades of lousy, unwatchable basketball will do that to you. A new century featuring one memorable season — in 2012-13 — and one memorable month — Linsanity — will make you wonder about a team’s karma.

And so it was Monday night, as Knicks fans watched along with everyone else as Kevin Durant limped off the Scotiabank Arena court in obvious agony, the initial diagnosis that arrived hours later — an Achilles injury, severity to be determined — delivering a fresh wave of agony to Knicks fans looking for a messiah – or merely a Messier.

But what if Durant’s injury — awful as that is for him, harmful as it is to the Warriors’ championship aspirations, despite their Game 5 stand — really isn’t just another in an endless series of unfortunate events aimed at Madison Square Garden?

What if the Knicks actually dodged a bullet?

The one nagging thing about all the momentum that seemed to build this year surrounding Durant-to-the-Knicks was this: By the time next season begins, he will be 31 years old.

The last time the Knicks built the entirety of their blueprint around a pending free agent was 2010, and the target was LeBron James, and that wound up tossed in the crowded trash pail of failed Knicks plans. But James was 25 years old that summer. Kawhi Leonard is the other white whale available in this season’s free-agent haul. He doesn’t turn 28 until the end of this month. Even Carmelo Anthony was only 26 when the Knicks acquired him.

Now, we aren’t saying Durant is George Blanda, or the WHA version of Gordie Howe. But 31 in the modern NBA is certainly long in the tooth. Bodies break down on the other side of 30, especially in a league fueled by young legs. When Durant first hurt himself, in Game 5 of the Western Semis against Houston, some initial reactions about the way his leg gave was that it looked like an Achilles issue, not a calf.

Imagine if Durant had sat the rest of the Finals, signed a fat deal with someone — for argument’s sake, since we’re plumbing worst-case scenarios, let’s say it’s the Knicks — and THEN the Achilles goes? That would make Antonio McDyess blowing out his knee on the eve of the 2002 season seem like an obscure footnote.

So perhaps it’s time to recalibrate.

Perhaps it’s time to think about the Knicks’ young core as a foundation, and not merely a placeholder. Assuming they keep the No. 3 pick — and they absolutely should keep that pick — they will be getting a terrific player, likely R.J. Barrett. Dennis Smith Jr. showed you enough last year to believe he could have a D’Angelo Russell-like breakthrough with the right guidance. Mitchell Robinson is one of the two or three most intriguing young players in the league, with a ceiling nowhere close to being determined.

Kevin Knox had a tough rookie year; you know who else had rookie struggles? James Harden. And Dirk Nowitzki. And Jimmy Butler. And — yes — Kobe Bryant, who also struggled at a painfully young age to adjust to life in the NBA. Knox may not blossom as the others did, but to write him off now, when he’s still two months shy of 20, is lunacy.

Does that team contend? Of course not. Maybe you make a what-the-hell run at Leonard, see if you can interest him in being Mr. Chips to the kids, but assuming that doesn’t happen, you take a deep breath, move forward with seven first-round picks between now and 2023, and save the cap space for a rainy day (and not — not, not, not — on a mid-level guy like Butler, Tobias Harris or Khris Middleton, just to say they did “something”).

The wild card, of course, is that you may still be unsure if you can trust Scott Perry and Steve Mills to negotiate this complicated gauntlet. That’s fair. It’s on the Knicks to prove they really have changed their methods and their M.O. It’s on them to pick the right players in the draft, and to figure out how to maximize their money.

And, not incidentally, it’s on them to prove that the days of tanking are over. There is no such thing as losing in the interest of winning. Not anymore. Not the way the NBA is set up. Never again.

Durant would have been tempting. He would have made the Knicks instantly watchable and, more important, instantly credible. But the Knicks reside in a new reality now. And if they are good at playing basketball poker, it could be a better one in the long run.

If they’re good at poker.