The 49ers would love to resembled the Jaguars on defense in 2018 – but they have a long way to go.

San Francisco will get an up-close look at the league’s best defense when Jacksonville comes to Levi’s Stadium on Sunday. It’s a unit defensive coordinator Robert Saleh is familiar with. He spent the past three says as the Jags’ linebackers coach.

He brought the scheme with him to the 49ers. It’s the same one that originated in Seattle under Pete Carroll that’s becoming more popular throughout the NFL. The Falcons and Chargers also run the same system, which relies on one-gapping principles up front, a single safety deep and mostly press cover-3 from the corners on the outside.

Saleh was asked if the Jaguars’ top-ranked unit offers a blueprint for the 49ers’ long-term vision on defense.

“I don’t know if you want to call it a method to the madness, but there is a clear vision of exactly what you’re looking for with each spot,” Saleh said. “There is a vision. We like to think we have an idea. … I’d like to say that the blueprint’s already kind of been created. It’s just maintaining your belief and conviction on what you see and know that works in the system and continue to build off that.”

But Jacksonville’s players are more important to the success than the defensive scheme. The talent level on that side of the ball is biggest difference between them and the 49ers.

The Jaguars are loaded while San Francisco is still in construct-and-develop mode. And Jacksonville has done it through free agency and the draft, taking multiple seasons to build a monster that’s carrying quarterback Blake Bortles to the third seed in the AFC.

They drafted cornerback Jalen Ramsey fifth overall in the 2016 NFL draft – and he’s already become one of the league’s premier defensive players. They signed cornerback A.J. Bouye to a five-year, $67.5-million contract last spring, who quickly became elite. Calais Campbell (four years, $60 million) was also signed last offseason and is having his best year as a pro.

Campbell (6-8, 282) has a career-high 14.5 sacks after spending his first nine years with the Cardinals. He’s a leading candidate for defensive player of the year and anchors the league’s best pass rush.

The 49ers have a similar player in DeForest Buckner (6-7, 291), although he’s used more along the interior while Campbell has transitioned outside. They don’t have a player like Ramsey, but would love Ahkello Witherspoon to develop like Bouye.

Replicating Ramsey could come next year in the draft if the team targets Alabama defensive back Minkah Fitzpatrick with its first-round pick. Fitzpatrick could likely play all five positions in the secondary and immediately fill a need at corner, where starter Dontae Johnson has underwhelmed this season and is headed for free agency.

What the 49ers don’t have is a defensive line filling up the stat sheet with sacks. Jacksonville has four players along the line with at least 7.5: Campbell, Yannick Ngakoue (11.0), Malik Jackson (8.0) and Dante Fowler (7.5).

San Francisco’s leading sack artists: Elvis Dumervil (5.5), Buckner (3.0) and four players have two apiece, including recent third-overall pick Solomon Thomas.

Kyle Shanahan is eager to see how his team — led by Jimmy Garoppolo — stacks up to the Jaguars.

“I look forward to it a lot, for our whole team. I do believe that they have as much qualities as anyone that it takes to win a Super Bowl; a top defense, a very good running game, a good offense, good special teams,” he said. “When you see a team like that on tape that you believe has that ability, it’s a good thing, it’s a good challenge for your team to go against them and see where you’re at.”