So when Chip Kelly offered him a chance to take the reins of UCLA’s reeling defense last February, Lynn was surprised.

“It came out of the blue,” he said. The prospect of such a major move admittedly made him uncomfortable. But Lynn, whose father, Anthony, also coaches at the NFL level, took the leap anyway.

“I just felt like I was ready to take that step, and I needed to get uncomfortable,” Lynn told The Times in August. “No matter what’s going to happen after this, I’m only going to grow.”

Lynn probably didn’t expect another leap so soon after that one. But after transforming a middling Bruins defense into one of college football’s best, another opportunity came knocking. This time, from the coach across town at USC. And with a much larger salary attached.

USC coach Lincoln Riley saw firsthand the foundational differences in UCLA’s defense after one season under Lynn. Riley was confounded by Lynn’s plans last month in the crosstown rivalry, as UCLA slammed the door on Riley’s dynamic offense, limiting the Trojans to three rushing yards, their lowest total since 2018.

Riley took notice. He was, at the time, still searching for answers on defense, a desperate pursuit that stretched back as far as his days at Oklahoma, where his commitment to defense was also regularly questioned. Now his failings loomed over all at USC, overshadowing any progress, and forced him to fire defensive coordinator Alex Grinch.

Riley understood, in light of Grinch’s exit, how much hinged on his next choice to lead the defense.

It took all of one conversation with Lynn to earn Riley’s confidence that the 34-year-old could succeed even though he only had one year of evidence at UCLA.

“We’re going to do everything that we can in this program to accelerate the process of us playing great defense at USC,” Riley said this week. “And whatever it takes to get that done from a development standpoint, from a staffing standpoint, from the way that we practice, everything here is going to be done with a defensive mind first.”

That would be a jarring shift for Riley, whose coaching reputation to this point has been staked entirely on his status as an offensive mastermind. But in conversations with Riley and new athletic director Jennifer Cohen before taking the job, Lynn said Tuesday that he could sense that renewed focus.

“They are passionate about playing elite defense here at SC by any means necessary,” he said.

A commitment to making Lynn among the highest-paid assistants in the sport certainly made that intention clear, as USC offered him a substantial raise from the $1.02 million he made per year at UCLA that put him closer to the $2-million mark, a person familiar with the search not authorized to speak publicly told The Times. Another source close to the search not authorized ot discuss it publicly confirmed Lynn was the only candidate who received an offer, but noted that Riley had serious conversations with other high-level candidates before returning to Lynn.

UCLA “made a push” to keep Lynn, according to Kelly, but “obviously weren’t in the ballpark” of what USC could offer. The Trojans weren’t the only ones courting Lynn, either, Kelly said.

“I think he’s a rising star in this coaching profession,” Riley said Monday, “and just every conversation that we had, felt more and more like this was the guy that we really wanted.”

As one of the top-paid assistants in the sport, he’ll be expected to show immediate progress at USC. But what that looks like under Riley, who has never fielded an elite defense, or in the Big Ten, USC’s new conference, is still to be determined.

Lynn ran a multiple 3-4 base system with the Bruins, one that utilized constant pressure up front to make quarterbacks uncomfortable, while playing largely a loose zone on the back end to limit explosive plays. His scheme was a major tenet of UCLA’s turnaround, as the Bruins finished sixth in the nation in sacks during the 2023 regular season, while allowing the seventh fewest plays of 20-plus yards.

That scheme probably sounds pretty good at USC, where the Trojans gave up more than twice as many explosive plays as the Bruins. But on Tuesday, Lynn said he didn’t believe in a static scheme. He prefers versatility at every level of his defense, but beyond that didn’t offer many details. He said he will adjust his plans to his based on personnel, a lot of which is likely to turn over in the coming weeks at USC.

For Riley, that willingness to adapt was one of the “non-negotiables” as he conducted his two-week search. At the top of that list of priorities, Riley said, was “the size and style that we play up front.”

That’s sure to be the refrain coming out of USC next season, as the Trojans trudge into a bigger, more physical conference in 2024 with — they hope — a bigger, more physical group up front. Lynn, at least, should grasp what the Big Ten demands of defenses, considering he spent four seasons at Penn State.

He didn’t have to review much of the roster to know what needed to change most.

“The Big Ten has big bodies on the offensive and defensive line,” Lynn said, “and that’s something that we need. To get bigger up front.”

Other sweeping changes are expected, including to USC’s defensive staff, though Lynn said he hadn’t given much thought to that yet. Hired just two days before the transfer portal opened, Lynn was already on the road recruiting Tuesday. He won’t coach the defense in the Holiday Bowl, but he’ll be watching closely during the next month, considering where to take USC’s defense next.

He’s already encouraged by what he’s seen.

“The first thing that sticks out,” Lynn said, “is the team is not that far away.”