Before this season, Todd Reirden had never served as an NHL head coach. He was handed the Stanley Cup champions. Here, try these guys on for size!

Those champs have 30 games left in the regular season, and the questions are piling up. Most notably: Does this new guy know what button to push and which lever to pull?

“That’s something that I feel has been my strength as a coach,” Reirden said Monday, “my feel for what the room needs at the right time and what our team needs to correct areas that are concerning.”

Uh, yeah, totally possible that’s the case. But, um, your Washington Capitals have lost eight of their past nine games. And they’re falling backward in the Metropolitan Division at a time that could be construed as critical: in the midst of their longest homestand of the season, just before they embark on their longest road trip of the season.

Add these optics: The Caps have essentially the same roster that won the Cup, but the coach who left town now heads the New York Islanders, the very team the Caps are looking up at in the Metro. So there’s an easy, quick-glance equation here, and Reirden knows it: The rookie head coach can’t get the same response the old veteran did, and Washington made the wrong decision in not meeting Barry Trotz’s contract terms, allowing him to resign and take over a division rival, while replacing him with someone who had never done it before.

“Anyone can draw the conclusions they want and say those things,” Reirden said, leaning on a water cooler outside the Caps’ dressing room after Monday’s practice. “But I know at the end of the day the amount of time and effort and work that I’ve put into trying to problem-solve and come up with a clear plan of how to win games, and then how to manage our team that’s dealing with the expectations and everything that goes along with being a champion.”

His self-confidence is unmistakable and plainly buoys him in this stretch. He has clearly decided to press a different button now, because in Sunday’s 1-0 loss to Boston — a team Washington essentially had the deed to, having beaten the Bruins 14 straight times — he benched center Evgeny Kuznetsov for taking a silly penalty. Tactically, he knows the game. He believes he knows how to manage the group, too.

But before you have done it — not in the minors, not as an assistant, but as the head man at the helm of a champion — can you really know?

“I don’t know,” said Brian MacLellan, the team’s general manager, the guy who hired Reirden. “We’ll find out. That’s hard for me to say. It’s results. It’s a results business.”

That’s the honest truth here. Reirden’s self-belief matters — for him. But for the rest of the hockey world, there are legitimate reasons to ask, “Can he figure it out?” Trotz was on the brink a couple of times during his wildly successful tenure as Washington’s coach. What you knew about Trotz then: He had handled those situations in the past and survived. You can’t say the same with someone who has never been in this spot.

“I think it’s different in that Barry has ways that he handles things,” MacLellan said. “He has the experience of handling it. Todd, he’s not going through anything a normal assistant coach wouldn’t be going through. . . . You’re going to get tested. I think we knew he was going to get tested. It’s up to him to show it. How do you predict that this assistant coach is going to be good at this? You can’t — until you’re in the heat.”

So here he is, in the heat. Reirden’s belief: He can handle it, and he will handle it.

“I know I have the skill set to get the players out of this,” Reirden said.

Now, there are a million things going on with the Capitals. Kuznetsov, who is among the best 10 players on the planet on those occasions when he decides to be among the best 10 players on the planet, has been maddeningly inconsistent. The Capitals’ defensive pairing of Matt Niskanen and Dmitry Orlov, so solid in last year’s Cup run, isn’t playing to its capabilities. The Caps lead the NHL in minor penalties taken and are tied for second in power-play goals allowed. They endured a suspension to key forward Tom Wilson and an injury to veteran T.J. Oshie, which required other players to push past their accustomed level of performance. Even before the seven-game skid that preceded the all-star break began, they looked gassed.

They returned from their break with an encouraging performance against Calgary, their only win in three weeks. And then they committed a pair of silly first-period penalties against Boston, played poorly for two periods and lost. Again.

The players are the same, a veteran group that knows each other. This is on the coach, right?

“I think it’s kind of paramount for us to hold each other accountable, especially when you have a guy like Todd, who’s a real positive guy,” sage defenseman Brooks Orpik said. “If he came in here and just started ripping guys, guys would see right through it. That’s not him. So there’s times where maybe he’s not going to do it, but he expects our group to kind of hold each other accountable.”

There are so many interesting dynamics here. Reirden was Trotz’s assistant, so he understands the personalities he’s dealing with. Now, though, the position from which he deals with those players has changed, so the relationship must, too. For a franchise, this also isn’t a normal transition from one coach to his former assistant, because the change came not following a failure but after the ultimate success.

“I think the trick for him is to push where he hasn’t pushed before,” MacLellan said. “How do you define, ‘I’m not an assistant anymore; I’m the head guy,’ and figure that out? This has been going on forever — in every sport.”

True. Right now, it’s happening in Washington with its hockey team, the one that won it all last spring and now is in a tailspin. The Capitals need to remember they didn’t become champions because they flipped a switch and decided to. They need to remember they worked and worked and worked until they got it right, and it clicked.

Coach Reirden, you’ve got 30 games before the playoffs to get it right.

Enjoying your new seat?

“I wouldn’t trade places with anyone,” he said.

Todd Reirden believes — sorry, knows — he can work the Capitals out of this funk. Now, the tough part: proving that to everyone else.