Mikel Brown Jr. walked into Barclays Center as a Louisville freshman and walked out as a Nets lottery pick — and the single biggest brick in Brooklyn’s rebuild. 

The Nets tabbed Brown with the No. 6 overall pick Tuesday, their highest in 16 years. Though tough luck saw them fall from the joint-best odds of winning the lottery all the way to sixth — missing out on the loaded top four — they still ended up landing the prospect many feel has the most upside outside of that quartet. 

“I just felt like I was the right pick. I think I fit into the system really well and what Coach Jordi [Fernández] has building with them,” said Brown, who gets to learn with last year’s five first-round picks and learn from veterans Michael Porter Jr. and Julius Randle on a team that’s trying to flip from tanking to competing. 

“I think it’s great. Obviously, you want to soak up as much knowledge as possible as a young player coming into this league. To be able to ask them and pick their brain on a lot of things, and to be able to play alongside them, it’s going to mean the world to me. And we’re going to try to bring a chip.” 

While Brooklyn suffered the ignominy of watching the cross-river rival Knicks do just that, the Nets are a long way off, just 20-62 last season. 

Without having next year’s pick, Brooklyn will look to take a step forward this upcoming season. Brown will be a big part of that. 

“Watching [Brown] play, just how dynamic he is as a playmaker and scorer, the pace at which he plays,” GM Sean Marks said. “He’s a cerebral player, has really great feel. It’s exciting to get a guy like that who has intangible skills as well. When you look at how athletic he is, the speed at which he can play, those things translate to our league. And then you get to meet the guy; he really has a chip on his shoulder, really has something to prove. Those are some of the things that stood out to us.” 

Though a back injury and too-tough shot diet led to an inconsistent freshman campaign, the 6-foot-4, 190-pound guard showed a combination of heat-check range, preternatural passing and downhill juice that they’ll hope to mold into an All-Star. 

“Just come in and be an impact guy right away and do what I do best; that’s creating for others and also creating for myself to score,” Brown said. “Being around veterans like Michael Porter Jr. that’s proven in this league, and Julius Randle is proven in this league, it’s going to help because I get to learn from them as well. 

“But I just feel like I plug in well, because they’re young. We’re going to go through some hardships together, we’re going to go through the good times together. I can’t wait.” 

He’ll need to add muscle, cut his turnovers, tighten his defense and improve his decision-making — both shot selection and risk management. 

But the rebuilding Nets can give him plenty of runway to do so. 

“We all talked about it,” Brown said of the improvements he has been told he needs to make. “Me overall just being a better basketball player in general, but obviously that tenacity, bring it on the defensive end every possession is big. 

“They showed me moments when you can be a really, really good defender if you really do take it seriously every possession. That’s something that they definitely told me. But other than that, they just told me to come in and be myself.” 

The Nets met with Brown at least three times — in Chicago at the combine, a workout in Brooklyn and even traveling to Orlando to meet with his family. 

“That was great, them just talking to me and getting to know me, and also me getting to know them as well. I thought there was something going on there, and you could kind of feel the energy and the vibe,” Brown said. “All smiles, man, just being a great person kind of stood out from both ends, and that’s going to go a long way. I’m ride-or-die for them.” 

A Nets team that already lacked size and traded away starting center Nic Claxton picked up an All-American big man late in the first round Tuesday night, drafting Iowa State’s Joshua Jefferson with the 28th pick. 

The 6-foot-9, 246-pound Jefferson did a little of everything to lead Iowa State to 29 wins, averaging 16.4 points, 7.4 rebounds, 4.8 assists. 

The Nets have been lacking the force and physicality that were so on display in the latter rounds of these NBA playoffs — traits Jefferson said he’ll provide. 

“I think the thing about my game that’s going to translate pretty quickly is my physicality,” Jefferson said. “The NBA is a physical game right now. You have to be physical in the playoffs to win, and that’s what I’m going to bring.”