The Washington Capitals just made my heart skip a beat. When they traded valuable draft picks Monday night to acquire (rent for the rest of this season) all-star defenseman Kevin Shattenkirk, I actually gasped.

There’s “going all in.” And then there is “GOING ALL IN.” The latter is when you call Lucifer and say, “Please allow me to introduce myself. I hear you buy souls.”

With the best regular season team in hockey again this year, with depth everywhere, with no obvious weaknesses, with every reason to think their chances to win the Stanley Cup are slightly better than everyone else’s (gales of laughter), the Caps just traded pieces of their future so they could have a fifth defenseman with exceptional ability. Folks, you need just four.

Washington traded for Shattenkirk in case someone gets injured months from now. He is insurance beyond insurance. He’s even a hedge against the rival Pittsburgh Penguins or New York Rangers trading to get him. It’s as if you bought hurricane insurance on your house, then also bought insurance on the insurance company — just in case a big storm drives ’em into bankruptcy and they can’t pay your claim. Sure, you paid twice. But when the wind starts to blow, you’re out on the porch yelling, “Blow, you bad boy, blow! You won’t get me this time!”

Wanna bet?

The Caps just traded pieces of their future so they could have a fifth defenseman with exceptional ability, Kevin Shattenkirk. Are only four needed? (Chris Lee/AP)

Sports fans think they get “broken hearts” when their teams lose, especially when they are favored to win and blow it. But they should see the expressions on the faces of athletes such as Jayson Werth, John Wall or Braden Holtby just minutes after they have been eliminated. They should see the faces of the owners and GMs who built the teams as they enter the locker room to say . . . what?

As Diane Keaton said to Jack Nicholson in “Something’s Gotta Give,” “You know what this is? This is heartbroken.”

[Svrluga: Kevin Shattenkirk trade shows only a Stanley Cup will be enough for Caps]

How scary is this Caps trade? It amounts to a sign in 10-foot-tall letters that says, “We have to win the Cup this year. This is our best team ever. And no matter how we manage it, we’re going to lose important players over the offseason. Yes, we’ll still be a contender. But if we don’t break the Caps Curse now . . .”

This is Washington’s version of the Chicago Cubs trading for closer Aroldis Chapman and his 103-mph fastball at the deadline last summer. Chapman and Shattenkirk aren’t comparable in the value of their roles. But the old-as-rock-’n’-roll message is identical: “If your broken heart needs repair, I am the man to see.”

So, let’s congratulate Caps General Manager Brian MacLellan and owner Ted Leonsis on their intestinal fortitude. Fear of failure is an enormous and inhibiting force in sports. Countless athletes have trouble completely “buying into” the coaching systems, or franchise ambitions or even the desires of their teammates. The deeper your commitment to a goal, the more you suffer if you fail.

Or we all tend to assume that’s how we’ll feel in defeat. Actually, “leaving it all on the field” may be the best way to cope with the possibility of loss. Doing so allows you to know afterward, deeply, that you couldn’t have done more or tried harder. But beforehand, such total commitment elicits first-parachute-jump fear.

MacLellan and Leonsis have made that leap. Along with Coach Barry Trotz, stars such as Alex Ovechkin and Nicklas Backstrom and thousands of fans, they are free-falling, trying to enjoy the sky dive of high expectation but, in the back of their minds, wondering whether the chute will open before they hit the earth. Especially because, for the past 33 seasons, including 26 postseasons, the ground has always won.

I have covered, at least in some part, almost every one of those 26 postseasons. And if I haven’t been in the locker room after at least 10 of the season-ending losses — are they always in the Igloo in Pittsburgh or filthy Madison Square Garden? — then I haven’t been in one.

So, the depth and seriousness of the Caps’ current conviction — their stubborn-willed forgetfulness about this collective past — have made my heart skip. How often does a team in any sport — knowing that, no matter how good it is, the chances are no better than 20 or 25 percent that it will be champion — make a public “Our Year” statement? I have placed both hands over my face and plan to watch the remainder of the NHL season through the cracks between my fingers.

MacLellan was asked by The Post’s Isabelle Khurshudyan: What is a successful playoff run for the Capitals these days?

“Winning a championship,” MacLellan said.

Will that expectation, so bluntly put, much as the Cubs spit in the eye of their 108-year World Series jinx last year, be a further burden of pressure to the Caps? Or will the addition of Shattenkirk, and the total we-have-your-backs stance of ownership and the front office, get everyone leaping over the boards together?

[Fancy Stats: All the ways Shattenkirk will turbo-charge Capitals’ playoff hopes]

For many years, too many years, every Caps postseason has felt like part of a continuum that’s connected to the past. It’s part of the same saga. The Capitals have never said, “This is the year.” They’ve said, “We’ll try again.” But as soon as the playoffs start, the same music plays in the background — usually spooky.

Someone had to rip up the old script and change the soundtrack. Someone had to take a bigger chance, risk the biggest of all Caps flops and trade away some of the future. Why? Because nothing else has worked. Or even come close.

If you make the playoffs 26 times, you should win about half of those series, then win the next round about six times and then the following round — to reach the finals — about three times, with one or two Cups to show for it. The Caps have reached the round of four just twice and lost the Cup, in a sweep, once.

To hell with it. Go all in. The Caps “probably” won’t win. No team ever reaches the status of “probably” before the postseason even begins. The Caps know it. That’s why it took even more guts to go for Shattenkirk. But sometimes the all-in team really does make it all the way. A curse ends. In Cleveland with the Cavaliers. On the North Side of Chicago. Who’s next? Who knows? Let’s not mention any names.

But whatever outcome awaits the Caps, this year just became very different.

For more by Thomas Boswell, visit washingtonpost.com/boswell.