SANTA CLARA, Calif. >> Robert Saleh’s firing Tuesday as the New York Jets’ coach immediately sparked theories that he might be needed back at his old office, as the San Francisco 49ers’ defensive coordinator.

Think beyond that. Keep looking at the Jets and how they fare without Saleh.

That’s because Jeff Ulbrich will be serving as their interim coach. It’s a title that screams “temp job” but also offers the San Jose native and former 49ers linebacker a first glimpse of himself as a head coach, with Aaron Rodgers at quarterback of a 2-3 team.

It could be an audition for an eventual homecoming with the 49ers — perhaps as their defensive coordinator next season if the Jets cut him loose, or perhaps as their head coach down the road.

Kyle Shanahan is not remotely on the hot seat, even though the 49ers have lost three of four since opening with a 32-19 rout of the Jets. But whenever Shanahan exits from one of the longest tenures by a 49ers coach, owner Jed York might want a familiar coach. York broke into the NFL at the same time as Ulbrich, when franchise control shifted from Eddie DeBartolo to York’s parents, Denise DeBartolo York and Dr. John York.

Ulbrich was a bruising, grinding linebacker from 2000-09 for the 49ers, a franchise his mom, Patty, served as a cheerleader in their Kezar Stadium days.

In confirming Saleh’s firing and Ulbrich’s promotion from defensive coordinator, Jets owner Woody Johnson released a statement that finished with this testimonial about Ulbrich: “He is a tough coach who has the respect of the coaches and the players on this team. I believe he along with the coaches on this staff can get the most out of our talented team and attain the goals we established this offseason.”

That isn’t exactly a long-term endorsement to stay with a perpetually chaotic franchise.

On Dec. 11, 2009, Ulbrich took a seat near the 49ers’ trophy case in their lobby and confirmed his 10-year playing career was over – but that, at age 32, he was eager to transfer his people skills and football knowledge into becoming a coach.

Earlier this year, Shanahan reportedly sought to poach Ulbrich from the Jets as a replacement for Steve Wilks as the 49ers’ defensive coordinator; Saleh and the Jets blocked that move, the San Francisco Chronicle reported last month. Shanahan, leading into the season opener, noted that “Brick’s a great coach and a good friend.”

Ulbrich’s hometown is Morgan Hill. His 120 games are tied for seventh-most by a 49ers linebacker. He made 501 tackles, two interceptions, a safety, and, most treasured, a spot on the 49ers’ 10-Year Wall for players with a decade of service.

Not bad for a 2000 third-round draft out of Hawaii by way of Live Oak High, San Jose State and Gavilan College.

Ulbrich was among Bill Walsh’s final draft picks ever. A few years later, when Walsh was a consultant, “he came up to me on the sideline and let me know he was proud of the way I’d become a pro,” Ulbrich recalled in that December 2009 interview. “I grew up around here and understood his legacy, so that’s one of the highest compliments I’ve ever gotten in football.

“I didn’t foresee people wanting me longer than that, to tell you the truth.”

Maybe he stays with the Jets. Maybe Shanahan never leaves the 49ers.

As for Saleh’s potential return to Shanahan’s staff with the 49ers, it would be too Jets-like for the 49ers to cut ties with Nick Sorensen only five games into his foray as the defensive coordinator. Plus, Shanahan already brought in an in-house option when he hired ex-Chargers coach Brandon Staley back in March. And Saleh has guaranteed millions coming from the Jets to rest and reboot before his next stop.

The Jets’ defense has allowed the NFL’s second-fewest yards and seventh-fewest points. Sorensen’s defense is 10th in yards, and 13th in points.

Still, the 49ers’ defense is not looking great situationally, not after surrendering 10-point leads in divisional losses to Los Angeles and Arizona over the past 16 days. Both the 49ers and the Jets are off to 2-3 starts, and losing teams are the ones that make changes.