A glimpse of The Duke in the Desert Saturday night was all that is required to understand the Rangers are likely to rue trading Anthony Duclair to the Coyotes the day before last year’s trade deadline, and for a long time to come.

But it does not necessarily follow that acquiring Keith Yandle for a Stanley Cup run was misguided, because the fact is that Yandle will be part of a pair of Stanley Cup runs, and when your team hasn’t won it all in two decades, you take your shot when you have it.

At the same time, though, it does not mean the cost of the transaction — that included a first-rounder going west — should be a factor, let alone determinative, in deciding what to do about Yandle, who is eligible to become an unrestricted free agent this July.

It is not so simple.

Yandle has not been the offensive force the Rangers anticipated, but he has shown flashes, most recently in Tuesday’s 3-0 Garden victory over the Candy Canes that followed a fine performance on Saturday against his former team.

Still, it will be about April, May and June for Yandle just as it will be for fundamentally every member of this squad. If there is no May, if there is no June; well, then and only then can judgement be rendered on the trade.

Remember this: the Rangers traded young all-time American Doug Weight to the Oilers for veteran Esa Tikkanen just ahead of the 1993 deadline and then missed the playoffs entirely. But a year later, Tikkanen was an essential part of the Blueshirts’ only Cup-winning team in the last 74 years.

Weight recorded 963 points after leaving the Rangers. Is there anyone who would want a do-over on that deal, or on the one at the 1994 deadline that sent another young all-time American, Tony Amonte (715 points after leaving New York), to Chicago for Stephane Matteau and Brian Noonan?

Asked and answered.

Two years ago when Ryan Callahan and Dan Girardi were entering the final season of their respective contracts, negotiations on extensions began over the summer and continued throughout the season. The same held true last year regarding Marc Staal and Mats Zuccarello.

Three of the four signed during their walk years. Callahan, the one who did not sign, was traded at the 2014 deadline.

But there have been no talks thus far between Rangers’ general manager Jeff Gorton and Yandle. Neither does there appear to be urgency on either side. There is no indication the Blueshirts will move Yandle if he does not sign an extension.

“We haven’t had any discussions with the Rangers,” Yandle’s agent, Jerry Buckley, told The Post on Tuesday. “There is no timetable as far as we are concerned.

“I know Keith likes it in New York and likes the team, but his entire focus is on having a good year and winning. I don’t anticipate there being a deadline for Keith to sign during the season.

“Both sides will have a clearer idea of how they want to proceed at the end of the year.”

If Yandle plays poorly, then the future will be pretty clear and it will be elsewhere for the 29-year-old. If he kicks it into gear and plays a significant role in a healthy playoff charge, well, then the future will be murky, as contradictory as that proposition may seem.

“I’m just focused on playing. I’m the kind of guy who leaves the business end to my agent,” Yandle said after the Blueshirts’ sixth straight victory. “Nothing has been brought to my attention [regarding talks on a new deal], and I’m fine with that.

“I’m having fun here. I just want to win.”

Yandle is operating under the final season of a five-year, $26.5 million deal with a $5.25 million cap hit that is divided equally between the Rangers and Coyotes under terms of the trade. It can be safely assumed that Yandle will not be taking a pay cut on his next contract.

The Rangers theoretically would have space to sign No. 93, but it defies logic that they would invest up to $5.5 million per long-term on him with lefty Ryan McDonagh in at $4.7 million per through 2018-19 and lefty Marc Staal in at $5.7 million per through 2020-21, the latter with a full no-move for another two seasons. Righty Dan Girardi is in for $5.5 million with a no-move through next season.

“There would be a lot to figure out,” Buckley said. “We understand. So let’s just let this year play out.”

Yes. Let’s.