SAN JOSE, Calif. — For years on end, the question hanging over the Islanders was when they would change their core, a process that properly began two seasons ago, when Brock Nelson was shipped to Colorado. 

It’s not over by any stretch, but you can see the difference across the dressing room, starting with the leadership group. Bo Horvat, the franchise’s first big acquisition who wasn’t involved in either conference final run earlier this decade, is the captain. Matthew Schaefer and Brayden Schenn are both wearing letters, having started their time with the Islanders a year ago. 

That change Islanders fans spent years begging for? Here it is. 

“I mean yes, it does [feel different],” Casey Cizikas told The Post after Tuesday’s practice at the SAP Center. “… The business we’re in, it happens all the time. I’ve been here long enough, I’ve had to say bye to a lot of friends I’ve made over my career. It’s just that kind of next man up mentality — I know you say it all the time, but you battle with the group you have in here. That’s the mentality. 

“It sucks seeing guys go that you’ve built relationships with over so many years. At the end of the day, it’s who’s in this dressing room that you’re going to war with every single night.” 

Seventeen games into the season, you can see the effects of change playing out in real time. 

The Islanders know the style of play that can get them winning results, having employed it to good effect over the season’s first month. It’s now about executing it with more regularity, while — they hope — integrating Mathew Barzal, Matias Maccelli and Ryan Pulock back into the lineup, and under the pressure that a losing streak, which hit four games after Monday’s overtime loss to the Sharks, brings. 

You could call it growing pains, or just the normal ups and downs of a season. But it all has a different tone than the Islanders of a few seasons ago. 

Horvat, Schenn and Schaefer all frequently speak on behalf of the group to the media as well, a small thing but one that — particularly in the case of the latter two — signals a difference in how the room operates. 

“Guys grow into roles where they feel comfortable,” Kyle Palmieri, another member of the leadership group, told The Post. “But a lot of this group and a lot of that leadership group, has been together for a while. And the guys we’ve added, it’s been a lot of experience, guys that have won. I think if you look at it, we all try our best to push each other and take that with us to lead the room.” 

Schaefer is young, but outgoing, and widely seen throughout the organization as a future captain. Schenn, a Stanley Cup winner in St. Louis, stuck out as a leader as soon as he got in the dressing room. 

“Right from the day we got him, he kind of assumed a leadership position, whether by choice or not,” Adam Pelech said. “It’s the way it is with a guy like him. And then Schaef, Schaef is just himself. He’s just himself every day. He doesn’t need to change to be a leader.” 

Horvat has worn a letter for a long time, but taking over the captaincy is, of course, a different thing. If there are differences in how the leadership group operates this season, though, that between him and Lee is one of the smaller ones. 

“I wouldn’t say they’re different at all,” Cizikas said. “They both leave it out on the ice every single night. They lead with their work ethic, with details, what it takes to be a professional. When guys see that, guys follow. They speak up when they need to, but it’s the way they compete on the ice, compete in practice, that really solidifies them as leaders and as captains. That’s something guys follow.”