Trust takes time.

For Kenny Atkinson and DeMarre Carroll, it took about six months. That’s when Carroll, in his first season with the Atlanta Hawks in 2013-14, offered Atkinson entry into what he called “Team Carroll,” his informal inner circle.

“I said thanks for including me. You want me to go get you a towel, or ice cream?” said Atkinson. “That’s the type, Jeremy (Lin) is the same way. I think we just have, there is a light-heartedness, there’s a sense of humor about it. We know how to bust each other’s chops. It’s different from other guys. Those guys are special, because you would enjoy having a bite to eat with them, or you would enjoy going on a trip to another country. They’re just people you want to be with, be around.”

So much so that, with Atkinson’s encouragement, Nets general manager Sean Marks brought Carroll to Brooklyn via trade from the Toronto Raptors over the summer. The reunion brings Carroll back together with a coach who was instrumental in the most successful stage of his nine-year NBA career.

The first time around, Atkinson was an assistant with the Hawks, working closely with players on skill development. He was beginning his second season in Atlanta when Carroll arrived in 2013.

The first four seasons of Carroll’s NBA career had been a struggle. Drafted in the first round by Memphis in 2009, he was traded to Houston the following season. He played five games for the Rockets and four for Denver before landing in Utah. With the Jazz, he found a solid role during the 2012-13 season, playing in 66 games. Most significantly, he showed enough to pique the interest of the Hawks, who were looking to fill a hole at small forward.

Atkinson found a player hungry to get better.

“I think he really bought into our player development program there,” he said. “You talk about a poster child, he was one of the guys that completely bought in. I think we gave him a lot of individual attention and he soaked it up. He gave us a competitive fiber that wasn’t there before he got there.”

“Kenny was one of those guys who always believed in player development, believed in my skill set and tried to minimize the game to allow me to do the things I do great at a very high level, rather than doing things that I really can’t do so well,” said Carroll. “It made me face reality and understand, you don’t have to do a whole bunch of things good. You can do a couple things great and do that above average and be successful.”

In his first season with the Hawks, Carroll started all 73 games he played. His minutes doubled. His 3-point shooting percentage tripled. His scoring average rose into double figures for the first time.

Together, Atkinson and Carroll worked on refining a 3-point stroke that Atkinson thought looked pretty good, even if it hadn’t been exercised much in games. They stressed defense and quick decisions — catch-and-shoot, slash aggressively to the basket. Don’t get into a spot where you needed a fourth or fifth dribble.

And they worked at it.

“We had a post-shootaround routine the day of the game,” said Atkinson. “I think it was eight to 10 minutes long. It was shots he was getting in the offense. Together, not just me telling him what to do, together we found this really cool routine. So shootaround would be over, he’d go to his basket. Just finding that niche with each guy.

“Some guys, it varies player to player and you have to find that chemistry. And once they start having some success, then it’s, you’re in. The trust is there. The personal relationship is there. You have your routine set. Then it was just doing it over and over.”

It was the second season in Atlanta that Carroll really considered the breakthrough. He averaged 12.6 points and 5.3 rebounds, plus career-high shooting percentages of 49 percent from the field and 39 percent from 3-point range.

The Hawks won 60 games and earned the Eastern Conference’s top seed in the 2015 NBA Playoffs.

“I think DeMarre was just like a sponge and he wanted to improve,” said Hawks coach Mike Budenholzer. “He wanted to grow. He wanted opportunities. I think Kenny and he took it and ran with it and see how far we could push DeMarre, how far Kenny could push him and put him in situations that maybe he hadn’t been in very much to that point. I think they both had a lot of fun with it and as an organization we reaped the benefits of both those guys’ work on a day-to-day basis.”

When the potential to acquire Carroll arose, Atkinson saw a player he trusted, who would fit into the way Brooklyn plays. He would also fit into the locker room, into the culture Atkinson and Marks are building, with his competitiveness and team-first attitude.

“It’s been better than expected,” said Atkinson. “Because in Atlanta, he had a voice in the locker room, he had a toughness. But he wasn’t the leader so to speak. Here, he’s in a little different position where he’s around a lot of younger guys. Knowing the person and the player, I thought he could do it, but I didn’t know until he got here. It’s been beyond my expectations in terms of how seamless it’s been. The basketball part I knew wasn’t going to be a problem. But this is a little different. Now you’re the senior leader. To lead a group, and he’s not perfect, he’s growing into the role, but much better than expected.”

Carroll might have offered a hint he was ready for that role before he even arrived in Brooklyn. Over the summer, he organized an alumni reunion game at the University of Missouri, where he had played for his uncle Mike Anderson and helped lead the Tigers to the Elite Eight of the 2009 NCAA Tournament and a school-record 31 wins.

With Mizzou struggling over the last few seasons, Carroll wanted to renew some enthusiasm and excitement around the program, and the return of successful hoops and football alumni helped draw a mid-summer crowd of over 6,000 people.

Brooklyn has felt like another homecoming. Back with Atkinson, playing the style where he found personal and team success in Atlanta — and also feeling healthy after struggling with injuries during two seasons in Toronto — Carroll is back in a comfort zone.

“It’s like a kid going off to college and then he comes back home and he knows where everything is,” said Carroll. “He goes to his room, he looks, it’s there and he knows what time we’re going to have dinner. That’s how I kind of feel. Went to college. Experienced something new. Came back home. And I’m happy to be back home.”

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