The NBA postseason is in full swing, but the Nets season ended two weeks ago — meaning they’re already planning and plotting for next season already.

Brooklyn general manager Sean Marks (not to mention coach Jacque Vaughn and team owner Joe Tsai) will be busy this summer with some big questions looming on the horizon. Trading Kevin Durant and Kyrie Irving in February closed their championship window, but there is plenty of retooling left to do and decisions to be made.

With Spencer Dinwiddie’s future with the team anything but certain (more on that later), it’s unclear what the long-term plan is…but the perfect plan is Damian Lillard. There are whispers that Brooklyn’s interest in the Portland star is very real. Lillard is close with rising Nets star Mikal Bridges, whom he has called his favorite small forward in the entire NBA and who works out in the offseason with Lillard and his Trail Blazers teammates Anfernee Simons and Nassir Little.

And after Lillard showed up unexpectedly to watch the Nets face Philadelphia in the first round of the playoffs, Bridges was asked about the All-Star point guard’s presence and coyly said, “I know people.”

The 32-year-old’s prodigious scoring, shot creation, leadership and high character are all traits the Nets need. He’s under contract for four years, and — making $56.6 million next season — Brooklyn would need to send Portland not only a trove of picks but also players making at least $36.5 million.

Logically, that would mean Nic Claxton or Ben Simmons, as well as some of their glut of wings (or the first-round picks they could get in return for them, to be rerouted to Portland).

Not very. Johnson is one of the few Nets who actually acquitted himself well in the first-round sweep at the hands of Philadelphia. And while this team isn’t good enough yet to prioritize postseason performance over regular-season performance, it definitely matters.

The sweet-shooting forward turned down a four-year, $72 million offer from the Phoenix Suns before getting traded, and after arriving in Brooklyn, multiple NBA sources told The Post that was the floor for re-signing him, but it would probably take more like $80 million.

That number has only gone up based on the way Johnson has performed, and if the Nets don’t lock him up during their window between the end of the NBA Finals and the start of free agency, he could land an offer sheet near or equal to his pal Bridges’ $90 million.

The fact that Johnson and Bridges are so close that they were dubbed “The Twins” back in Phoenix only adds to his job security here in Brooklyn, as does the fact a team that wants to acquire him in a sign-and-trade would face being hard-capped.

Versatile bigs and shot-creating point guards.

Claxton emerged with a career-year and was fifth in Most Improved Player voting, but the starting center still needs help. Any team as switch-happy as Brooklyn by default creates a weakness on the defensive glass, and the Nets know they can’t subsist with just one reliable big man. “Without a doubt we need to make some changes in terms of adding some size,” Marks said. “I think [Vaughn] said it, add a little nastiness.”

And while Dinwiddie is the only veteran point guard or proven shot-creator on the roster, the Nets were listening to offers on him right after they acquired him. They elected to keep him, but who knows what happens over the summer with Dinwiddie on a $20.4 million expiring deal. He’s extension-eligible for four years and $128 million starting Aug. 7, which seems a bridge too far.

Brooklyn could use replacements or complements. With Dillon Brooks banished, could the Nets ship a wing (Royce O’Neale, Dorian Finney-Smith) to Memphis for Tyus Jones or Brandon Clarke?

Essentially, let it ride. Simmons is a three-time All-Star, and the only player on the roster to have been voted into the midseason showcase. Getting him healthy and as close to his former self as possible is a top offseason priority. Right now, with two years and $78.2 million left on his contract, his value is at a low ebb, and attaching much-needed draft picks to move a distressed asset makes little sense (unless he helps bring back a star like Lillard).

Simmons had a microdiscectomy in May 2021 and his nerves should take 18 months to fully heal, meaning roughly a month into next season. But after being shut down in February with an impingement, sources told the Post the Nets should know early this month whether Simmons needs another surgery.

Both Nets sources and others close to Simmons expect him to avoid another operation, the latter adding, “The group around Ben has noticed a complete change in Ben’s focus and mentality through this rehab and how he’s attacked it and engaged with everything.”

Adding to the sense of optimism, Australian national team head coach Brian Goorjian told SEN (the national sports radio network) Friday that “there is a really strong chance” Simmons could play for the Boomers in the FIBA World Cup, tipping off Aug. 25. That’s roughly a month before the Nets open camp.

The Nets can only hope so, because that’s how they’ll get value from him.