With the Los Angeles Lakers mired in the worst years in franchise history, owner Jeanie Buss has turned to Magic Johnson to lead them back to championship contention.

And she removed her own brother from his job to do it.

Buss fired general manager Mitch Kupchak on Tuesday and put Johnson in charge of basketball operations. Jim Buss also was dismissed as the Lakers’ executive vice president of basketball operations in a major shake-up of the struggling team’s front office.

Jim Buss retains his ownership stake in the team, but Jeanie Buss has final say under the structure set up by their late father, Jerry Buss. She used it to chart a new course for the 16-time NBA champion franchise, which has the NBA’s third-worst record at 19-39.

The Lakers are almost certain to miss the playoffs for a team-record fourth straight season, and they posted the worst record in team history during each of the previous three years.

‘‘It was such a hard to decision to make, that I probably waited too long,’’ Jeanie Buss said in an interview on Spectrum SportsNet, the Lakers’ television network. ‘‘For that, I apologize to Laker fans. Now, with clarity and direction, and after talking with Earvin, a change was needed.’’

Just 19 days after Johnson returned to the Lakers in an executive role, Jeanie Buss decided the Hall of Fame point guard will be the Lakers’ decision-maker in basketball operations despite no experience as a personnel executive.

Johnson is the Lakers’ president of basketball operations, reporting directly to Jeanie Buss, and it appears that Johnson is moving quickly to surround himself with a team to help his transition.

According to a person with knowledge of the situation, prominent agent Rob Pelinka has begun informing his clients that he plans to leave Landmark Sports Agency to become the Lakers GM. The person spoke on condition of anonymity because the Lakers have not commented on the front office search.

‘‘The status quo wasn’t acceptable,’’ Jeanie Buss said. ‘‘It wasn’t Lakers basketball. It wasn’t what this organization stands for.’’

Johnson said he will put aside his numerous business obligations and his role with the Los Angeles Dodgers, in which he holds an ownership stake, to concentrate on his work with the Lakers. The charismatic former superstar spent the morning fielding calls from general managers and preparing for the trade deadline in two days.

‘‘I'm coming back to an organization that I love,’’ Johnson said. ‘‘The timing is right. It was time to put aside my businesses and focus on the Lakers’ business.’’

Johnson acknowledged the Lakers were involved in trade discussions for All-Star center DeMarcus Cousins, who went from Sacramento to New Orleans. Los Angeles has plummeted out of contention after an encouraging 10-10 start under Luke Walton, but the rookie coach got a strong vote of confidence from Jeanie Buss and Johnson, who said he ‘‘loves’’ Walton as a coach and an example of the Lakers’ championship culture.

Kupchak is a former Lakers center who had been employed by the franchise in some capacity since August 1981. He had been the Lakers’ GM since 2000, studying under Jerry West and eventually succeeding him.

Kupchak had been in the Lakers’ front office for 30 years, including the last 17 as general manager — the longest current stretch running a front office in the NBA.

Rockets get Williams

The Lakers swung their first deal of the Magic Johnson Era, agreeing to send Lou Williams to the Rockets for Corey Brewer and a future draft pick.

Brewer’s agent, Wallace Prather, confirmed the terms of the trade. Neither team immediately revealed the trade publicly.

‘‘Thanx for the love L.A., I've enjoyed my stay,’’ Williams wrote on Twitter.

Williams led the Lakers in scoring at 18.6 points per game, playing off the bench. Brewer was averaging 4.2 points for Houston.

And while the draft pick will help the Lakers’ future, the Rockets just got deeper.

Williams has scored more points off the bench than anyone else in the NBA this season — and Eric Gordon, the newly crowned 3-point shootout champion at All-Star weekend — is No. 2 on that list.

Reserves have three games of 35 points or more this season, all by Williams, all in a dazzling seven-day span in early December.

He had 40 points against Memphis, 38 against Utah, and 35 against Phoenix.

Williams has been to the playoffs six times with three teams, seeing action in 41 postseason contests. He’s under contract for $7 million next season.

Brewer is also under contract for next season, at about $7.6 million.