49ers' Tatum Bethune details how Fred Warner fueled his growth

San Francisco 49ers linebacker Tatum Bethune is preparing for his second NFL season, and he's already showing signs of significant progress. The former seventh-round pick has turned in solid preseason performances, backed by analytics—an 81.6 tackling grade against the Denver Broncos and a 79.7 run-defense grade against the Las Vegas Raiders, according to Pro Football Focus.

The 49ers may lean on Bethune as a key rotational linebacker in 2025, and the 24-year-old says much of his offseason development can be credited to All-Pro Fred Warner.

Bethune admitted that he took a hard look in the mirror during his self-evaluation. That meant reviewing what he put on tape during his 51 defensive snaps last season.

"I compared it to Fred's film, and I thought it was trash," Bethune told reporters Wednesday. "So, this offseason, I tried to be a sponge and do everything Fred does, just from the way he carries himself off the field to on the field."

Linebackers coach Johnny Holland fueled that growth, sending Bethune hours of film to study—much of it of Warner. Bethune returned to the facility early—in March—eager to work with coaches and refine his fundamentals.

"I'm not all the way there yet, but I see a huge difference, even in just the way I take my first step or my first few shuffles," he said. "And I compare it to last year—it's a big difference. I've still got a long ways to go."

Playing faster than the stopwatch

At his 2024 pro day, Bethune ran a 4.77-second 40-yard dash, raising questions about his speed. But both he and his coaches insist his game speed is far superior.

"He plays much faster than [that]," defensive coordinator Robert Saleh said. "Kind of like [LB Dre] Greenlaw. Greenlaw ran a molasses 40, but his GPS suggests differently."

Bethune agreed, noting the difference between track speed and football speed.

"Football speed and 40 speed, them two different things," the linebacker said. "If you run a 4.4 in the 40 but don't run a 4.4 on the field, then, yeah."

Saleh also highlighted Bethune's versatility, pointing ou t that he's capable of playing all three linebacker spots and could step into the Mike linebacker role if Warner were unavailable.

Nutrition and discipline: Warner's challenge

Warner's mentorship went beyond film and footwork. He challenged Bethune to overhaul his diet and hydration before offering further advice.

"Fred told me he's not telling me anything else until I get my nutrition and my hydration together," Bethune recalled. "I took that serious because he's right. If I can't do the simple stuff right, then what makes me think I could go in there and do all the things he's buying to help his body be better?"

Once Bethune got past that obstacle, he was able to observe Warner's example and did his best to emulate the veteran.

"I did the same thing, and I felt the difference," Bethune said. "And I understand now that those are things I need to keep improving on, and that's going to help me go far in this league."

Bethune admitted his sweet tooth might have been the toughest obstacle. He loves candy, and found one treat particularly challenging to give up.

"I love Swedish Fish," Bethune said. "But yeah, I gave it up."

Paying it forward

Now entering Year 2, Bethune is also taking on a leadership role with the newest draft pick in the linebacker room—Nick Martin, a third-round selection.

"Even though we're the same age, I kind of treat myself like he's my little brother," Bethune said. "I make sure I'm in his head before we go out on the field. And in the Raiders game, he had a hell of a game, and I just told him, 'Just be you. Run and hit.' And that's what he did, so it's just good to see Nick just keep doing it and getting better."