Bradley Beal’s decision to sign an extension with the Wizards shook up the NBA landscape, dashing contenders’ hopes of prying him out of Washington to build a new Big 3.

But the Nets are confident they already have the making of one anyway, without mortgaging their future. They’re convinced Caris LeVert can take that leap forward and become a third star on a championship team.

“Why not?” said Kenny Atkinson, pointing to Toronto’s Pascal Siakam, taken in the same 2016 draft. “I don’t really talk about other teams, but Siakam’s a case where here’s a guy in one year jumped and was a difference-maker.

“Obviously Kawhi [Leonard] was great and [Marc] Gasol was great, but here’s a guy that came from being a real role player to a Big 3 or a Big 2 or whatever you want to call it. I know Caris wants to get in that conversation. We want him in that conversation. We know that’s where the real progress will be made.”

After averaging just 7.3 points in 2017-18, Siakam vaulted to 16.9 points and 6.9 boards last season to win NBA Most Improved Player — and help Toronto to its first title. He gave Leonard a viable running mate. Can LeVert do the same for Kyrie Irving — and Kevin Durant, whenever he returns?

Prying Durant out of Golden State ended the era of NBA Big 3s. Now the Nets, Lakers, Clippers and Warriors will see dueling dynamic duos.

Some have suggested LeVert’s team-friendly three-year, $52 million extension in August could still let the Nets use him as the linchpin of a trade for a star such as Beal. But scouts and players The Post talked to feel he has All-Star potential himself.

“Just continuing to take steps. Baby Mac is the GOAT,” Spencer Dinwiddie said. “He’s got a patient style, he’s very crafty around the basket. He’s an underrated passer. He’s going to be a great player in this league for a long time, and he’s already showing it.”

In reality, all LeVert may need to take a huge step forward is to just stay on the court. His foot woes have been well-chronicled, and he missed three months last season after a nasty dislocation.

This preseason, LeVert was poked in the eye just a minute into the first game against the Lakers in China, and didn’t return. But it doesn’t appear serious, and he was full-go at practice leading up to Friday’s preseason finale against Toronto.

“It feels a lot better. Still a little red. I just got poked the second, third play of the game. I’ll be fine, though,” LeVert said. “[I’m] pretty comfortable. I feel like I’m getting closer to the season form. Can’t wait to get out there. It’s going to be fun.”

LeVert was placed on the same team as Irving during Thursday’s practice, and he was looking forward to getting some chemistry going with his starting backcourt mate.

“Super-exciting, man,” LeVert said. “We haven’t played together in a real game. … So can’t wait to see it in a game and can’t wait to get more comfortable.”

The Nets have a while to develop that comfort level with a core that appears fairly fixed.

Seven players are under contract for at least three years. Even with Durant and Irving holding player options for the fourth year of their deals, this roster will essentially be set for a while by NBA standards.

“Caris, can he go from really good to great? That’s the challenge for us as coaches, to push these guys in that direction, because that’s where the big time results will come,” Atkinson said.

“The main pieces of the group are here for four years. Well, I guess they have player options, so three years. [But] it’s a long time,” Dinwiddie said. “You pretty much have your team for a very long time in terms of the NBA world, so it’s about coming together.”