The Nets’ transformation might have been three years in the making, but the sudden climax that transpired Sunday night when they reached agreement with top free agents Kevin Durant, Kyrie Irving and DeAndre Jordan was overpowering. It was a paradigm shift that elevated expectations and dramatically altered the perception of the organization.

But here are a few words of warning from departing veteran free agent DeMarre Carroll: “Now, I think the biggest key for the Nets is to continue their culture and stand by their culture. Although you’ve got the top guys and sometimes you have to be lenient because they’re the best players, they’ve still got to stand strong on their culture and have some veteran locker-room guys.”

Since he, Ed Davis and Jared Dudley, three veteran leaders, are leaving as free agents, Carroll told Newsday on Tuesday he believes it’s vital that the culture they helped to develop be maintained by the incoming stars. “When those guys [Durant, Irving and Jordan] come in, they’re going to be the older guys,” Carroll said. “You don’t want them to come in and kind of not appreciate what you already established. That’s going to be the biggest key.”

Reflecting on where he was when traded two years ago by the Raptors in what widely was portrayed as a salary dump to where he is now, having agreed to a two-year deal worth $13 million with the Spurs, Carroll admitted he’s surprised by how quickly general manager Sean Marks and coach Kenny Atkinson orchestrated such an improbable turnaround.

Although the Nets were coming off a 20-62 season that was worst in the NBA, Carroll had played under Atkinson when he was an assistant in Atlanta. “I was happy going to a system I felt like was going to prosper,” Carroll said. “They believed in culture, and they believed in doing it the right way. When I came to Brooklyn, to say that I thought it was going to happen this quick? No. But I knew it was going to eventually happen, and I think it happened at a great time.”

Under Marks, the Nets don’t just pay lip service to the notion of “culture.” They live it. From Carroll’s perspective, it not only is reflected in how they developed young players such as Caris LeVert, Spencer Dinwiddie and Joe Harris but also how they found roles for knowledgeable veterans.

“Look at myself and Jared and Ed, how they stretch our careers out further, made us get more games and more years than what we thought,” Carroll said. “When I came from Toronto, they kind of put my career back on track and made me into a solid, productive role player. Even D’Angelo [Russell], people used to say he was a bad locker room guy, but then he got here.”

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Russell, of course, was sent to the Warriors in a trade for Durant and a future first-round pick, but he wound up with a four-year max deal worth $117 million that might not have been expected when the Lakers traded him to the Nets. Davis signed a two-year deal with Utah, and on Tuesday, Dudley agreed to a one-year deal with the Lakers.

When Carroll joined the Nets, he was coming off two injury-plagued seasons, but he got healthy and put up career-best numbers after working with the Nets’ performance team. He is convinced that was a major attraction to Durant, who suffered a ruptured Achilles tendon in Game 5 of the NBA Finals and will miss the entire 2019-20 season.

“You’ve got to hand it to Sean because he went out and spent the bucks to get those guys over here from everywhere across the globe,” Carroll said of the performance team. “I think guys like Kevin Durant and Kyrie really looked at that as a plus because Brooklyn really is ahead of the curve when you consider their performance team.”

Marks grew up in the Spurs organization, and Carroll said he chose them as his next team even though he had one better financial offer because he understands the value of that culture. He’s proud to help turn the Nets into a playoff team, and he believes Atkinson will forge strong relationships with his new cast of stars to build on that success.

“Kenny is a player’s coach,” Carroll said. “He likes to communicate with his players and ask for their opinions. He’s going to have to lean on K.D. and Kyrie and DeAndre. It’ll be good.

“They just have to understand to come in and be ready to work, and hopefully, there’s more success for Brooklyn. I’m always going to be a Brooklyn Nets fan.”