It was no surprise where to find Kenny Atkinson on the afternoon when everything about basketball in Brooklyn changed forever. This was June 30, a Sunday. Old gym rats never really leave the gym, so Atkinson was on the eighth floor of the Nets’ regal headquarters on 39th Street and Second Avenue, overlooking Gowanus Bay.

The seasons never really end for a gym rat, it is all one long basketball conversation, always. Of course, on this day, there was only one subject on the lips of anyone who truly cared about basketball:

Where was Kevin Durant going?

Sometime that day, the news would leak somehow, somewhere, and some coach was going to be given one of the great gifts of all time: a generational talent, entrusting the rest of his prime years to his hands.

Atkinson figured: That’s going to be one lucky coach.

“We didn’t have any special heads-up, so I was in the dark,” Atkinson says. “I’ve been in this before with other teams when I was an assistant and I’ve seen it go the other way so many times. So I was pretty skeptical. I wasn’t a believer until …”

He laughs. “Until I heard it.”

He let the shock wear off. Let the reality sink in. And had a moment of clarity, if not a full-blown epiphany.

“Oh wow. How am I going to coach these guys? This is going to be different …”

Well … yes. And no.

In an instant, everything changed … and nothing did. In an instant it was Kenny Atkinson — lifetime grinder, lifetime gym rat, the Point Guard Whisperer — who was that lucky coach delivered Durant (to say nothing of All-Star point guard Kyrie Irving). Three years after inheriting the ruins of a dust-bowl roster, three months after a brief but boisterous cup of coffee in the NBA playoffs for the first time, the rules of engagement had changed for Atkinson.

Just not the rules of who he is, and what he is.

“I always felt like I got along with every guy on every team I’ve been a part with, whether you’re the 17th guy or the first guy,” Atkinson said. “I can’t change who I am, because the guys will spot that right away. You have to be yourself. And even once I realized that we were getting some incredible players, that’s what I knew. I had to be true to who I am.”

It was the work ethic that served him best as a player, as a high-school star at St. Anthony’s on the Island, in college at Richmond, and all over the world thereafter. It was a pure commitment to the grind that made him one of the NBA’s coveted assistants for years, and later one of its more attractive sleeper candidates to run his own show.

It’s what allowed him to endure 20-62 and 28-54 his first two years on the job here, what allowed him to retain a calm even as last year’s team started 8-18 and seemed determined to lose every close game it played. And what allowed him to fully appreciate what happened after those first 26 games, when the Nets finished 34-22, took a game off the Sixers in the playoffs, one of the more feisty and fun teams in the whole league.

It’s what guides him now.

“I think sometimes people expect to look at me and see Billy Martin on the sidelines,” he says with a wide grin. “But that’s not going to happen. That’s not me.”

As much as anything, Atkinson was struck by the instant validation Durant and Irving’s decision lent to everything he and GM Sean Marks have tried to incorporate into the Nets’ infrastructure. We are beaten by the lead-pipe cliché of “culture” so often in modern sports that it can lose its meaning. But that really is what happened here. Atkinson is convinced.

“They had so many choices, both of them,” Atkinson said. “We were an improving team, we had a good year but it’s not like we were perceived at being at the ultimate, elite level. Normally that’s what superstars do, they look at the top three teams, the top five teams. But they saw we’d gained enough momentum and showed enough improvement where they would choose us.”

But there was more.

“It says a lot about word of mouth, too,” Atkinson says. “It’s a player’s league, and the players in the league talk to each other. So when a Joe Harris talks about what we’re building here, or a Spencer Dinwiddie, other players listen to that. They hear that. And those are conversations that helped us, too.”

The coach knows how unique his situation is. With Durant on the shelf for most of the foreseeable future, he has a different mission than Erik Spoelstra did, when the great Heat teams were assembled 10 years ago, or even the Cavaliers team that Irving helped lead to a title a few years ago, and the Celtics team he played for last year that failed to meet enormous expectations.

They are, in essence, an elite team on a layaway plan. There are enough pieces in place that they could be very good this year if everyone stays healthy — say, 45-48 wins and a playoff series win — but the real payoff is still in the future. Of course, the Nets are no longer a cute team on the come, either. And they are also no longer an afterthought in their own city.

“It’s really a perfect piece of timing,” Atkinson said. “Can you imagine if this had happened when I first got the job? Instead it feels like the right place and the right time for me, and for all of the guys. We’re ready to keep building this thing.”

The old gym rat smiles, looked out at his team, finishing off a hard scrimmage on the eighth floor of their fancy new gym in the heart of Brooklyn.

“All you ever ask for as a coach is to be able to coach good players,” he says. “What can a guy like me ask for that’s better than this?”