SANTA CLARA, Calif. - In search of some much-needed stability at defensive coordinator, the San Francisco 49ers are turning to a familiar face.

After a 16-day search, the Niners are re-hiring Robert Saleh as defensive coordinator, a league source told ESPN on Friday evening. Saleh, who coordinated San Francisco's defense from 2017 to 2020, is heading back to San Francisco after a three-plus year stint as the New York Jets head coach.

Saleh's hiring comes after the Niners immediately sought a reunion with him soon after moving on from previous coordinator Nick Sorensen. Niners coach Kyle Shanahan confirmed that Sorensen was out as defensive coordinator (though the team hopes to retain him in a different role) on Jan. 8.

At that season-ending news conference Shanahan said he was hoping to find an experienced candidate for the job and though he was open to scheme change, he was more focused on finding someone who could problem solve on the fly when things weren't going as well.

"I want someone that kind of meshes with what I believe in, but I also believe in that you've got to fit to come up with the best thing possible that fits our situation right now," Shanahan said on Jan. 8. "So, that'll be talking about our personnel, the roster, a lot of things like that and what their plan would be with it."

One day after that press conference, the 49ers announced that they had completed an interview with Saleh, who finished last season in a consulting role for the Green Bay Packers. From there, Saleh still had interviews with the Las Vegas Raiders, Dallas Cowboys and Jacksonville Jaguars for their head coach positions, which left the Niners waiting for an answer.

While Saleh didn't get much traction for the Raiders or Cowboys jobs, he was in the mix for the Jaguars job, making for some tense moments around the 49ers facility as they awaited the outcome. When Tampa Bay Buccaneers offensive coordinator Liam Coen re-emerged as a top candidate there on Thursday, everything again pointed toward a Saleh-Niners reunion.

While Saleh has been away from the 49ers for the past four years, there's plenty of evidence that he and Shanahan can not only work together but achieve success. During his previous run as the Niners coordinator, Saleh's defense turned into one of the best and most productive units in the league after some early hiccups.

When Shanahan took over in 2017, he hired Saleh as his first defensive coordinator, a job Saleh had never held before that. In 2019 and 2020 combined, the Niners ranked 10th in points allowed per game (21.9), third in defensive efficiency (63.15) and defensive expected points added (73.52), second in yards allowed per play (4.9) and tied for ninth with 47 takeaways.

Upon Saleh's departure to the Jets, the Niners quickly pivoted to linebackers coach DeMeco Ryans, whom they'd been grooming for the job as Saleh's head coaching candidacy gained steam.

Like Saleh, Ryans enjoyed plenty of success running the Niners defense from 2021-2022 but San Francisco's defense hasn't been able to recapture that prosperity in the past two seasons under Steve Wilks and Sorensen.

Shanahan moved on from both coaches after just one season but noted in early January that part of the reason it's been difficult to replace Ryans has been the fact that the Niners reached the NFC Championship Game and Super Bowl to end the 2022 and 2023 seasons, respectively.

Those late finishes limited the candidate pool, an issue Shanahan didn't face this year after the Niners dropped to 6-11 with a defense that ranked 29th in the NFL in points allowed per game (25.6) and 31st in red zone efficiency allowed (68.4%).

But even with plenty of time to evaluate options and interview multiple candidates (Lions defensive passing game coordinator Deshea Townsend and Niners assistant head coach Brandon Staley also received interviews), Shanahan quickly zeroed in on the coach he knows as well as any in the league with Saleh returning to the place that put him on the NFL coaching map.

"He's a teacher and he's going to give you his thoughts but the beauty with him is he's not afraid to have those heated conversations to try to get across what he's trying to get across," Saleh said of Shanahan in March. "But also, the respect to give you the leeway to make the best decisions for what you think needs to get done. He will challenge you. And when he challenges you with conviction, you'll know it."