This is an interesting development.

In addition to Robert Saleh, the 49ers have interviewed Detroit Lions defensive pass game coordinator and defensive backs coach Deshea Townsend.

Saleh obviously is the 49ers’ first choice because he coached this defense already and he was highly successful. In addition, he has head-coaching experience with the Jets where he also built an elite defense.

But Saleh also has head-coaching interviews lined up with the Jaguars and the Raiders, which means there’s no guarantee that the 49ers will get him. So they need a backup plan.

Enter Deshea Townsend. He’s intriguing because he’s nothing like Saleh. He’s not a Saleh knockoff, which is what Nick Sorensen was. He called a vanilla defense with lots of zone coverage and minimal blitzing. Townsend comes from the Lions who are known for playing man-to-man coverage and bringing heavy pressure. Hiring him would signal a drastic schematic and philosophic shift for the 49ers.

In addition, the Lions currently have one of the strongest cultures in the NFL, as opposed to the 49ers who had more drama and dysfunction than just about any other team this season. Townsend could help rebuild the culture that Shanahan, Saleh and DeMeco Ryans built together years ago.

Townsend played cornerback in the NFL for the Steelers under Bill Cowher and Mike Tomlin, so he has tons of pedigree. His only drawback is his lack of experience. He never has been a defensive coordinator or called defensive plays. Which means he would be a rookie learning on the job, just like Sorensen.

Still, Saleh and Ryans were rookies when they became defensive coordinators for the 49ers and they were excellent. Maybe Townsend could be similar.