Lately, the Islanders can do no wrong at Barclays Center. They have a four-game winning streak, which includes victories over quality opponents in the Kings and Red Wings.

The bigger test comes Thursday when the Metro Division-leading Capitals, with a 20-point edge over the third-place Islanders, arrive in Brooklyn before the Islanders play nine of their next 10 games on the road in what could be a season-defining stretch.

The Islanders still have to qualify for the playoffs and any long-range success in the postseason will likely require them going through the Capitals. The Islanders are 0-2 against Washington, which includes a 4-1 loss at home in January and a deflating 3-2 loss earlier this month in Washington when Alex Ovechkin scored the game-winner with 2:40 remaining in regulation.

Jaroslav Halak was in goal for both losses. The statistical advantage continues to widen in favor of backup Thomas Greiss, who is 10-3-2 at Barclays and 16-6-2 overall. Halak is 3-7 in his last 10 starts and was pulled twice. He is 8-5-1 at home and 13-12-4 for the season.

So, who starts against the Capitals? “I know, but I’m not going to disclose that now,’’ coach Jack Capuano said Wednesday after practice at Northwell Health Ice Center in East Meadow.

The Islanders believe the time has arrived for them to beat the Capitals. “It’s a huge game for us in the standings and for our confidence as a group,’’ Kyle Okposo said. “If we come out and play the way that we can we feel like we can beat them. It’s time to go out there and prove that.’’

advertisement | advertise on newsday

John Tavares added, “There’s no secret, they’ve proven themselves to this point. In playoff time they’re going to be one of the teams obviously everyone’s going to look to to be one of the favorites. You’re going up against a great team with a lot of great players. You have to raise your game to have success and obviously to win.’’

While Ovechkin is the undisputed sniper for the Capitals, Tavares said there is equal concern with center Nicklas Backstrom, whom he called “so underrated, it blows my mind really. Playing against him almost each and every shift of the playoffs last year he’s probably one of the best two-way centermen in the game. Everyone thinks of him as just a great passer and playmaker, but he’s just so smart. He doesn’t give you a whole lot of time and space. He’s very strong on the puck and very good in the faceoff circle. He’s got the complete package.’’

Notes & quotes: Despite Calvin de Haan’s lower-body injury, the Islanders did not immediately call up a replacement from Bridgeport. “It’s obviously going to be a question mark going forward [with de Haan],’’ Capuano said, “but we should know more [Thursday] morning. We don’t want to prematurely make that call until we know for sure.’’