The Capitals still face an uphill climb. But they have started to believe.

“I think we always felt confident in our team, but it’s nice to show that confidence and work to our advantage all the time,” defenseman John Carlson said.

Washington arrived in Toronto in late July — more than 3½ weeks ago — but hadn’t shown a full buy-in effort during the playoffs. The team expressed its desire to improve after each outing, but it never fully came to fruition until the latter two periods of Tuesday night’s win.

“Obviously, any comeback is exciting, but I think it’s more the way we played the second and third periods,” Holtby said. “That’s the key to our ability to come back and win this series. If we play every period like that, it’s going to be really, really hard to beat us. Because we had everyone going, everyone pulling on the same rope, and our job now is to make sure that filters over into the next game.”

So what changed?

Maybe it was the Alex Ovechkin-driven haircuts and facial hair changes that sparked the camaraderie within the group. Maybe it was the team bonding session after the Game 3 loss, in which Lars Eller said the Caps “had some good times, had some laughs and already starting rebounding for the next game.”

Or maybe the Capitals finally went out and had fun, as Evgeny Kuznetsov said after Tuesday night’s game.

“We started enjoying the hockey game, and that’s what gives us success,” Kuznetsov said. “I believe that it’s very hard to defend when guys wear you down for 45 seconds, 50 seconds. Yeah, maybe we don’t shoot a lot of pucks, but at the same time we give respect to your linemates when you share the puck, and that’s maybe not NHL typical hockey, but that’s how we’re supposed to play.

“If we’re going to play like that, we’re going to have job, we’re going to have fun and we’re going to have success.”

Kuznetsov’s own success Tuesday also stood out. With Nicklas Backstrom (concussion protocol) out for Game 4 and rookie Brian Pinho used sparingly, Kuznetsov was double-shifted for a good portion of the game. Already centering the top line between Ovechkin and Tom Wilson, he also skated alongside Ilya Kovalchuk and Richard Panik in an adjusted third line.

Kuznetsov skated 22:42, the most of any forward Tuesday night. With his best performance in the postseason, he now has two goals in the series. Coach Todd Reirden said Wednesday that he expects Backstrom to be a game-time decision for Game 5 on Thursday.

The Capitals are still facing a grim reality: The Islanders hold a 3-1 lead in the series.

“We put ourselves in a tough spot,” Reirden said Wednesday. “We didn’t deserve to win the first three games, and last night was the first game we put the work in, put in enough effort and commitment in, and [Ovechkin] was a leader in that department in terms of what he said and how he went about it, and that is what has to be matched to give ourselves a chance to continue in this tournament and in this playoff.”

Only three Capitals players have scored in this first-round series: Ovechkin, Kuznetsov and T.J. Oshie. The team has scored only three goals during five-on-five play. All three have come from Ovechkin, who tallied his 69th postseason goal Tuesday night. Meanwhile, the Islanders have scored 10 goals five-on-five, with eight players contributing.

“Certainly, I have confidence in this player,” Reirden said. “We’ve all seen him score goals. We’ve seen him score goals in playoff games and big games before, and he’s right on the cusp. . . . You’re not going to score every chance you get, but you’ve got to get yourself opportunities, and that’s what he’s doing, and we’re going to rely on him to do that again [in Game 5] if we want to continue.”