Who steps up alongside NFL’s top LB duo of 49ers Fred Warner, Dre Greenlaw?

SANTA CLARA — One year, it’s Fred Warner being called the NFL’s best linebacker by Aaron Rodgers.

Another year, it’s Dre Greenlaw intercepting Tom Brady, then daringly seeking his autograph on that football.

They are kings of the NFL linebacker world, and they are instrumental to the 49ers’ defense in another season with Super Bowl expectations.

“They wanted to consider themselves as the best linebacker group in the world about three years ago,” linebackers coach Johnny Holland said. “I always tell them it’s a tough task.

“If you consider yourself that, you’ve got to show it not just on Sundays but every day, and those guys are willing to work every day. They are the hardest work in linebacker group I’ve been around.”

Beyond Warner and Greenlaw is a group of talented but mostly untested linebackers who could be summoned at any instant to keep things grooving. Azeez Al-Shaair did that the past few seasons, and he’s now making a full-time audition with the Tennessee Titans via free agency (one year, $5 million).

As the 49ers reconvene for training camp, the fiercest competition could be among their linebacker corps, where understudies to Warner and Greenlaw also must win roster spots with special teams prowess.

All these linebackers share a common trait, however.

“I know, just for our system, we need athletic linebackers that can play in space,” Holland said, “and they are more convert guys, that have been safeties or secondary players in high school and college, who are coming in and playing linebacker for us.”

The 49ers, essentially, want hybrid linebackers. Yes, they must still be capable of playing “in the box,” shedding blocks and making tackles. The passing-fancy NFL also requires linebackers who use their quickness, speed, hands and eyes to make plays in coverage.

The 49ers’ ability to do all that makes them the No. 1-ranked linebacker unit, according to Pro Football Focus, which graded it best in pass coverage and second-best in run defense.

“They want to be the best in the world,” defensive assistant Nick Sorensen said. “You know, and that’s kind of been the mantra for a while around here with the ‘backers.”

A decade ago, Patrick Willis and NaVorro Bowman were leading the 49ers’ defense to NFC Championship Games and Super Bowl pursuits. Warner and Greenlaw are the modern-day one-two punch.

But what about the others? Here is a scouting report:

Oren Burks: Filled in for three starts last season (seven tackles in an Oct. 30 win at the Rams) and could be the front-runner as the No. 3 linebacker (strong side). He’s a mainstay on special teams (12 tackles last season) and serves as the 49ers’ NFL Players Association representative.

Demetrius Flannigan-Fowles: His conversion from college safety has come along so well that he could be the top backup behind Warner and Greenlaw. He had 18 special-teams tackles last season, including three in the playoffs.

Curtis Robinson: An ankle injured sidelined this Stanford product at the start of last season, then he played in three games, returned to injured reserve, and finished the season on the practice squad.

Marcelino McCrary-Ball: After latching onto the practice squad as an undrafted rookie last year, he immediately took a seat next to Warner in meetings, and that’s helping this year as he gets auditions at “Mike” linebacker. “He’s a very hard worker and, you know, he was a nickel in college, never really placed stack linebacker behind the ball,” Holland said. “You’re kind of guessing, ‘Can he play behind the ball?’ ” So far, so good.

Dee Winters: Drafted in the sixth round, TCU’s captain “has a lot of tangibles we look for in our linebackers,” Holland said. “He can run, has got great speed, instinctive, he can find the ball.”

Jalen Graham: This potential seventh-round steal has 6-foot-3 length, deceptive speed and a background similar to Warner’s blending defensive back and strong-side linebacker skills. He could be their latest seventh-round steal.

Mariano Sori-Marin: Undrafted rookie from Minnesota is a prototypical inside linebacker whose intelligence and athleticism fit the 49ers’ system.