LOS ANGELES — The New York Yankees signed Manager Aaron Boone to a three-year contract with a team option for 2025 on Tuesday, making it clear they believe that the reasons for their recent lack of postseason success lay elsewhere. Boone’s contract expired after the 2021 season, and the Yankees let three key members of his coaching staff go this month.

“I thought Aaron Boone was part of the solution, not a problem — not the problem,” said Yankees General Manager Brian Cashman, who said there was “never a doubt” in his mind that Boone would return.

“To be quite honest, if he were entering the free agent market, I believe he’d be the number one managerial candidate in baseball,” he said. “There’s a number of different vacancies, and we would be going to market looking for someone like him.”

Boone took over as Yankees manager in 2018 and is 328-218 since, with a .601 winning percentage in four seasons that is the fifth highest among all major league managers ever. His teams have made it to at least the American League Division Series every season but this one, when they lost to the surging Boston Red Sox in the wild-card game. But the Yankees don’t play to make the division series every year, and Boone has led just one of his teams to the AL Championship Series — never beyond.

“There’s a ladder you have to climb and I acknowledge we’re not climbing that ladder, especially this last year, anywhere high as we expected to be climbing,” Cashman said. “We just got to find ways to reconfigure and get past it.”

In what turned into an hour-long post-mortem evaluation, Cashman pointed to shortstop as an area of need this offseason. The Yankees have multiple prospects who may someday fill that position, which could affect whether they bid on any of the top shortstops available who may be seeking long-term deals. But Cashman seems determined to make a move.

He said the Yankees also will evaluate their catching situation — namely, whether Gary Sánchez’s flashes of excellence can turn into a consistent gleam, or whether they should look elsewhere. But more than anything, Cashman said he felt moves meant to improve the Yankees’ athleticism and ability to make consistent contact, such as signing DJ LeMahieu long-term or trading for first baseman Anthony Rizzo at the deadline, did not have the desired effect.

“We went backward in categories that certainly we didn’t see coming or expect. Obviously, two of our areas of strength were supposed to be our bullpen and our offense going into the season,” Cashman said. “Then obviously we went to the trade deadline and tried to reinforce and stuff, and our offense completely went backward from typically a top-two offense in runs scored on a yearly basis to finishing 10th in our league this year in a lot of different categories that were flashing red lights of alert, alert, alert. There are problems here.”

But the 48-year-old Boone, he felt, was not one of them. And after a trying up-and-down season that visibly aged the former Yankees postseason hero, who admitted he wasn’t sure whether he would return after New York lost that wild-card game, Boone said he thinks he can be part of the solution and continue to improve, too.

“I feel very confident in my ability, and still do, in getting the most out of people. That is on me, to help them reach their potential,” Boone said. “One of my jobs is tapping into that, and that is one area I need to continue to get better.”

The Yankees seem determined to surround Boone with new people to help him do that. Hitting coaches Marcus Thames and P.J. Pilittere were among the three coaches whose contracts expired that the Yankees decided to replace. The other was third base coach Phil Nevin, one of Boone’s closest confidants.

“That was a couple of tough days for me. I even talked to Phil about coming back,” Boone said. “Those are tough conversations you have. But that is the difficulty of this business.”

Boone’s return means the Yankees’ job will not be among those open this offseason as the San Diego Padres, New York Mets and St. Louis Cardinals hunt for managers. The Cardinals recently fired Mike Shildt because of “philosophical differences” with the front office. The Padres tend to hire managers who have a history with General Manager A.J. Preller, a pattern some think indicates a desire for constant oversight on the part of Preller and his staff. Boone seemed frustrated when he was asked about the way the front office influences his decision-making.

“We’ve built this straw man that this is what happens and we call up and ask for permission to push this button,” Boone said. “At least in my experience, and I’ve only been doing this with one organization, it’s not the case.”

For now, Boone will stay with that organization as it heads into what seems destined to be a massive roster overhaul this offseason. Cashman said he and his staff will evaluate every position, even the ones with established players. That is what they did with their manager, he said. They decided he will be a part of their future.

“I think I can help lead us to the top,” Boone said. “That’s why I’m here. That’s why I came back. That’s why I originally signed up.”