The Nets’ coaching staff suffered a brain drain last offseason that proved costly. It could happen again this offseason, because assistant Steve Clifford is in the picture for the Kings’ head-coaching job.

Clifford isn’t a full-time assistant coach for the Nets, he’s a consultant. Still, he has provided an experienced veteran sounding board for head coach Steve Nash, who just wrapped an up-and-down drama-filled second season on the job. Clifford interviewed Sunday in California a source told The Post, and is still believed to be in the mix for the job in Sacramento.

“We’ll see if anyone has a job opportunity to be a head [coach],” Nash said after the Nets’ first-round playoff sweep at the hands of Boston. “But I really enjoyed working with my staff. They’ve been unbelievable at staying together this year.”

Current Warriors assistant Mike Brown and former Golden State coach and current ESPN analyst Mark Jackson are among the finalists for the Kings job, according to ESPN.

The 60-year-old Clifford was the head coach for Charlotte from 2013-18, and for Orlando from 2018-21, before signing on as a Nets consultant. He was also a Knicks assistant from 2001-03.

Mike D’Antoni had been on the Kings’ interview list and is currently in the mix for the Hornets’ opening according to ESPN. D’Antoni was part of the Nets’ brain drain last summer. D’Antoni, who coached Nash with both the Suns and Lakers, also was a head coach with the Knicks and Rockets before joining Nash’s initial staff as a de facto offensive coordinator for a year.

Ime Udoka served a similar role on the other end of the court for the Nets’ 2020-21 team, which came a Kevin Durant toe (and Kyrie Irving and James Harden injuries) away from beating the eventual champion Bucks in the Eastern Conference semifinals.

But D’Antoni stepped away after the season and Udoka landed the Boston head coaching job. Harden missed D’Antoni’s pick-and-roll expertise, and Udoka guided the Celtics past the Nets and his former boss.

The ugly first-round exit brought Nash and his staff under scrutiny, although Durant said he fully expects the coach to be back. Nash thinks so too.

“Yeah I loved doing this and love these guys, love my staff, love all the departments,” Nash said. “Really have a great working environment, really enjoyed it and want to continue doing it.”

D’Antoni is also expected to meet with the Hornets, along with former Nets head coach Kenny Atkinson (now a Warriors assistant), ex-Nets assistant Sean Sweeney (now a Mavericks assistant and one of the game’s rising young minds) and the Bucks’ Darvin Ham.