If this is the way the Islanders are going to keep playing, and if they keep getting goaltending like this, they are going to be better than most people thought.

It was an air-tight performance Monday afternoon at Barclays Center, a 4-0 shutout of the Stanley Cup-contending Sharks that was impressive in stature and comprehensiveness. That includes the tidy 35-save shutout from Robin Lehner, making his first start of the season and his first start for the Islanders since signing as a free agent this summer. It was also the first shutout for a goalie making his Islanders debut.

“I thought he was solid, and I thought our team was solid,” coach Barry Trotz said. “To me, it’s a team win. We do everything as a team, I thought everybody contributed through the lineup, but it always starts from the net out.”

One of the biggest questions for the Islanders (2-1-0) going into the season was what type of goaltending they were going to get. Thomas Greiss started the first two games of season, an overtime win in Carolina and a loss to the Predators at home Saturday night. But Trotz went to Lehner for this one, and the team in front of him made it look pretty easy against the Sharks (1-2-0), one of the most skilled units in the league even before the team acquired Erik Karlsson in a blockbuster summer trade.

“It’s defensive structure, but above all, it’s effort,” said captain Anders Lee, who opened the scoring with his second power-play goal of the season 14:34 into the second period. “You can tell it’s there. Everyone takes pride in it. It’s all five guys on the ice and the goalie. Everyone is pulling the same rope right now.”

Compared to the team under Doug Weight — or even Jack Capuano, for that matter — the Islanders always had offensive firepower but always allowed far too many goals. Last season, they were last in the league in goals against.

But if the Islanders keep playing the way Trotz wants them to, with a discipline that is as impressive as it is new, they could end up bothering some people in what was thought to be a predictable Metropolitan Division.

“We’ve been saying it all along — we believe we have people in here [who] can get into the playoffs and have success,” said Matt Martin, who got a big goal at 13:02 of the third period to make it 3-0 when he finished a nice feed from Valterri Filppula, who now has two goals and an assist three games into his Islanders tenure. “There is a lot of talent in this room. There are a lot of two-way, checking forwards, forwards that are going to give it their all. I think it’s a good blend.”

So the recipe has been laid out for how the Islanders can have success, and it starts with a defensive structure that thus far has been stout. They seem consistently to have players back and in the right position, and the only chances San Jose got were from loose pucks in front.

And when they got those chances, Lehner was in perfect position to make the saves look easy.

“He was tight. He was moving. He wasn’t reaching for stuff,” Trotz said. “I know their shooters were seeing a wall. Any goaltender — a guy that’s 6-foot-6 or a guy that’s 6-foot — when they’re tight and confident, they always look like a wall to the shooters.”

Of course, it’s only been three games for the Islanders under Trotz. And it’s only been one game for Lehner. But it was an impressive game, supplemented by a floating goal from Scott Mayfield at 5:16 of the third to make it 2-0 — set up by a hit and a screen from Cal Clutterbuck — along with an empty-netter from Casey Cizikas.

The team now has five days without a game before it starts a week-long road trip in Nashville on Saturday night, then moving on to the three California teams. Right now, the Islanders look pretty good — but it is still early.

“It’s three games, but we feel we can be even better than we’ve been so far,” Martin said. “Obviously this road trip coming up is going to be a good test for us.”