It was a little nervy at times, but the San Francisco 49ers got the reunion they wanted, rehiring Robert Saleh to be their defensive coordinator.

Mike Silver, Matt Barrows and Zack Rosenblatt of The Athletic reported the Niners are expected to hire Saleh for a second spell as defensive coordinator, a role he occupied from 2017 to 2020 before leaving to be the head coach of the New York Jets. The Jets fired Saleh last October.

Saleh had long been considered the frontrunner for his old job with the 49ers after Nick Sorensen was relieved of his duties.

But Saleh attracted significant head coach interest during this cycle and appeared to be in a great spot to land the job with the Jacksonville Jaguars after favorite Liam Coen pulled out of the running.

However, Coen performed a U-turn following Jacksonville's decision to part with GM Trent Baalke, who once infamously occupied the same role with the 49ers, freeing up San Francisco to confirm the return of Saleh.

Rehiring Saleh was clearly a priority for the 49ers, who officially interviewed just one other candidate, Detroit Lions defensive passing game coordinator and defensive backs coach DeShea Townsend. Brandon Staley was named as an in-house candidate by head coach Kyle Shanahan.

Betting on Saleh not getting a head coaching job was a risk by San Francisco, but it has paid off, and he can now focus on the task of reinvigorating a defense that experienced a steep decline in 2024, finishing 26th in Expected Points Added per play and 29th in success rate in its lone season under Sorensen

The personnel from his first spell is very different, with Nick Bosa and Fred Warner the only defensive players under contract for 2025 that were on the team the last time he was the coordinator in 2020.

But Saleh's track record says he should be able to turn around a defense that still has All-Pro talent at all three levels. The 49ers were second in DVOA, which measures per-play value, on defense in 2019 when they went to Super Bowl 54, and only dropped to seventh in 2020 despite a plethora of injuries in the pandemic season.

After a difficult 2021 from a defensive perspective with the Jets, Saleh's defenses finished sixth and third in DVOA in 2022 and 2023, with extremely sub-par play on offense preventing those efforts from delivering playoff football.

Saleh's track record in delivering defensive production is undoubted. However, his success in his second spell with the 49ers will hinge not only on his ability to get the players to execute the scheme — which has its foundations in Seattle’s Cover 3 defense but has grown more complex from a coverage perspective — at a high level, but also his aptitude for calling well-timed tweaks to the system, changeups that were all too lacking under Sorensen.

“I love the scheme that we’ve had here. I think it’s one of the hardest things to go to when you’ve got the right guys in the right spots," Shanahan said of the defensive system at an end-of-season press conference. 

"But, I do think people adjust to schemes, and I think you have to adjust too depending on your personnel. And I think that was a tougher thing for us this year. Just going into the season, it was a little bit harder than past seasons and some of the injuries we had, I think, made it really tough for Nick. 

"And I thought he got better trying to adjust and do different things, but I do think that’s something that definitely, I’m not saying you’ve got to change schemes, but you have to have the ability, the history and the knowledge of how to change some stuff up when you’re in some certain situations. And I think that we do need that more going forward."

Adapt or die. That has been the way of the NFL for a long time. Saleh grew into the ideal defensive coordinator for the Niners during his first spell. Now his challenge is to prove he has the ability to adjust and do it again with an almost entirely different set of players. His success will have a great bearing on the Niners' hopes of returning to contention in 2025.

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It can be done, but it’s very tough.