It wasn’t that long ago that Rondae Hollis-Jefferson was the kid in the room.

He was the rookie, on a roster with players with 10 and 14 years of experience in the NBA. With another who would end up playing more seasons with the Nets than any player in franchise history.

Like a lot of 20-year-olds – maybe more than most — Hollis-Jefferson was all energy and enthusiasm, with a personality he didn’t always know how to turn off. During a summer gathering of NBA rookies for a league photo shoot, his fellow rookies voted him the league’s funniest guy among the incoming class.

“When I first came in, it was just like, ah, he’s a jokester,” said Hollis-Jefferson. “A lot of people thought I was immature. I heard some people passed up on drafting me because of that. So yeah, it was kind of like, that kind of hurt me in a way.”

When he got to Brooklyn, he struggled with the transition after two years at the University of Arizona.

“I was seeking out how to fit being on a team with guys old enough to be my dad,” said Hollis-Jefferson. “It was something different for me. I was kind of quiet, but I also felt like, I have my own voice, which kind of got me into trouble sometimes.”

“I just didn’t understand it,” he added. “It took a lot for me to grow out of that, saying things impulsively.”

If Hollis-Jefferson has changed, so have his surroundings and his circumstances. As the 2017-18 NBA season opened, he was, remarkably, the longest-tenured Net on the roster at the start of his third professional season.

A month after his 23rd birthday, Hollis-Jefferson is one of nine Nets on the team’s 15-man roster aged 25 or younger. As he’s grown up, the team around him has gotten younger.

“I’m kind of like still the same person, but just more controlled,” said Hollis-Jefferson. “I’m more, you can just tell the way I carry myself, how I talk to people. It feels good to be able to do that. People take you more seriously.”

It’s all part of what coach Kenny Atkinson has seen since arriving prior to the 2016-17 season. A growing maturity, coupled with physical development, that has made Hollis-Jefferson one of Brooklyn’s most important and productive players.

“He’s still open, kind-hearted, extrovert,” said Atkinson. “He’s naturally attracted to people. But I do say he’s kind of drawn the line with his work, and I think when he steps on the floor he’s become much more focused, much more dialed in. And again, just keeping his emotional controls, young player, he’s really improved in that area.”

As Hollis-Jefferson developed a better fit in the locker room, he created one on the court. That was a process that required its own patience. The role Hollis-Jefferson grew into defies expectations about players that fit his profile, in different ways.

At 6-foot-7 and 214 pounds, Hollis-Jefferson starts at the ‘4’ – or power forward – spot, a position that a generation ago required a player at least three inches taller and maybe 30-plus pounds heavier. But even as the league has trended smaller, Hollis-Jefferson is pushing those boundaries.

One of the reasons the NBA has gone in that direction is to add shooting range to the position. But, on a team that fires away from beyond the arc at a rate that exceeds nearly every other team in the league, Hollis-Jefferson built his offensive game around drives, post-ups and mid-range jumpers.

Hollis-Jefferson takes 90 percent of his shots from inside of 19 feet, split almost evenly between attempts at the rim and jumpers from 5 to 19 feet.

“He’s found his niche,” said Atkinson. “I think he’s found his niche with the drives, driving to the rim where he creates. He’s improved his finishing rate, and then he gets to the free throw line a ton. He’s playing to his strength in that sense. And then his mid-range game, his elbow game, we call it the Karl Malone spot game, right off the post, then you can face up and keep guys honest. Then when they come out on him he can drive it.”

On his first media day as a Net in 2015, Hollis-Jefferson brushed aside doubts about his perimeter shooting prowess by describing himself – with a grin of course – as a “mid-range assassin.” But even at the time his confidence in that part of his game was waning.

He found a fresh start with advice from a legend. Before his NBA career with the Los Angeles Lakers, Kobe Bryant starred at Lower Merion HS outside of Philadelphia, a rival of Hollis-Jefferson’s hometown high school in Chester, a town on the shore of the Delaware River south of the city.

Bryant’s own career began before the NBA’s 3-point revolution, and the long-range game was rarely a major part of his own offensive repertoire. He encouraged Hollis-Jefferson to find a home at a spot where he’d always been comfortable, in the elbow area at the end of the foul line.

“To get that advice from your childhood idol, it was big for me,” said Hollis-Jefferson. “That’s something I just worked on. Plays from the elbow. Plays from the mid-post. Kicking it out. All these things that are happening that I do, these are the things that I worked on.”

The elbow offered options; to drive, to flick in a jumper from a comfortable range, to dish to a cutting teammate as defenders committed to him on the edge of the paint. So did posting up outside the paint, from a similar distance of 10-to-15 feet, where he could turn and face the basket after receiving the ball and consider the same possibilities.

Those spots became the starting point of Hollis-Jefferson rebuilding his confidence in his offensive game. In his third season, he’s nearly doubled his scoring average and increased his numbers across the board while earning bigger minutes and greater responsibility.

He’s gotten more comfortable with himself on and off the court. When the Nets opened HSS Training Center in 2016, Hollis-Jefferson moved to Brooklyn before his second season. He’s come of age in the borough. Two years after wondering how he could fit in, he feels at home.

“I kind of have a sense of Brooklyn,” said Hollis-Jefferson. “The community. Even the people that work in the Barclays, they’re just so familiar with seeing me. Brooklyn’s a part of me. That takes place into the locker room, into how you interact with people. I’m not only giving them Rondae, I’m giving them what Brooklyn gave me. The love they gave me. The different personalities they gave me. I’m just showing the guys in the locker room that this is what you’ll face in Brooklyn. Embrace it. Love it. Because they’ll love you back.”

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