LOS ANGELES — With Marcus Mariota and Jameis Winston leading two top-notch offenses into the Rose Bowl on Thursday, almost everybody expects this College Football Playoff semifinal to feature plenty of points.

Oregon’s Don Pellum and Florida State’s Charles Kelly are in charge of preventing that seeming inevitability, but these two rookie defensive coordinators are used to doing difficult work.

“We’re not going to be changing the game plan,” Pellum said. “After 13 games, you’re not going to change it. We just have to execute.”

There’s a certain similarity to the paths followed by Pellum and Kelly to Pasadena. When the Ducks and Seminoles needed new defensive coordinators early this year after the departures of two high-profile predecessors, both schools shunned mercenary hires and promoted veteran assistant coaches to the most prominent jobs of their careers.

Neither defense had a spectacular season under its new management, struggling with injuries and occasionally producing lamentable defensive results. Yet both clearly have been good enough to earn a national title shot, and Kelly and Pellum both express pride in their work — albeit tinged with the awareness that their jobs are about to get a whole lot tougher.

“We knew there would be some challenges, but at the same time, I think our guys have stepped up,” Kelly said. “Are we the same team? No. But I’m very proud of what our guys have done and how they have hung in there together and fought through.”

Kelly had moved from Georgia Tech to Florida State just one year before his promotion, taking over when Jeremy Pruitt left the Seminoles for Georgia after only one season in Tallahassee — and just eight days after Florida State beat Auburn in Pasadena, California, for the national title. Kelly is Jimbo Fisher’s third defensive coordinator in three years, starting with Mark Stoops’ departure for Kentucky.

Florida State led the nation in scoring defense and interceptions last season during its national championship run. Kelly had the daunting challenge of replacing a flock of soon-to-be NFL players, including Jacksonville linebacker Telvin Smith, St. Louis safety Lamarcus Joyner, Chicago linebacker Christian Jones and Baltimore teammates Timmy Jernigan and Terrence Brooks.

“That’s five guys right there that have started in the National Football League as rookies this year,” Kelly said. “I think you can see the development of a lot of guys (as replacements).”

Several Seminoles took on larger responsibilities in their teammates’ absence. Kelly’s defense relies less on constant quarterback pressure than Pruitt’s defense did, partly in concession to injuries, but remained among the nation’s toughest units in red-zone defense. Like the offense, Florida State’s defense has repeatedly struggled early and finished strong in games.

“It’s been really fun to play for (Kelly),” Florida State linebacker Terrance Smith said. “I love what he’s done this year. It’s different than last year, but his halftime adjustments have helped us finish up games. Pruitt was a little more aggressive, blitzing more. I love to blitz, but I can’t be mad.”

Pellum worked his way up the hierarchy at Oregon for 23 years, patiently helping Mike Bellotti and longtime defensive coordinator Nick Aliotti, who retired after 17 seasons in charge.

Oregon was among the Pac-12’s top defenses in each of the past two seasons under Aliotti, thriving in the high-scoring conference and earning national respect. The Ducks have improved down the stretch, holding four of their past five opponents under 20 points.

Oregon appeared to be peaking for the postseason after embarrassing Arizona’s offense in the Pac-12 title game — but Pellum’s task got tougher this month when All-American cornerback Ifo Ekpre-Olomu was ruled out for the Rose Bowl with a knee injury in practice.

“We lose a very talented player, but we (also) lose a spiritual leader there,” Pellum said. “A guy with a lot of experience, a guy that’s been in the battle. So we all have to pick up the slack.”