Raiders’ rookies impressive on defense

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On the football field, you hear things that aren’t said or viewed as compliments anywhere else. Take Raiders rookie defensive lineman Mario Edwards Jr.

He is “twitchier” than they thought he would be, defensive coordinator Ken Norton Jr. said.

“Edwards is doing some fantastic things,” Norton said. “The things we saw on the film when we scouted him, he’s a lot twitchier, he’s fast, he moves pretty good.”

Edwards, weighing 279 pounds after being as high as 310 at Florida State, has been lining up at both defensive end and defensive tackle at training camp in Napa.

“We’re very, very, very, happy with his development,” Norton said. “And he’s only getting better.”

Another rookie who has been doing well on defense is linebacker Ben Heeney, a fifth-round choice from Kansas. He blocked a punt in Sunday’s practice and then broke up a pass in a scrimmage Monday.

All while being served a slice of humble pie.

Defensive end Mario Edwards Jr., (97) warming up during rookie camp at the Oakland Raiders headquarters in Alameda, Calif., on Fri. May 8, 2015. Defensive end Mario Edwards Jr., (97) warming up during rookie camp at the Oakland Raiders headquarters in Alameda, Calif., on Fri. May 8, 2015. Photo: Michael Macor, The Chronicle Buy photo Photo: Michael Macor, The Chronicle Image 1 of / 1 Caption Close Raiders’ rookies impressive on defense 1 / 1 Back to Gallery

“I found out what it truly means to be in the league, and I got put on my butt one time,” Heeney said. “I am not really used to that.”

Not the biggest linebacker at 6-foot, 230 pounds, Heeney had a knack for being around the ball in college, and the Raiders want to see more of the same.

“They just think I am a hard worker and a hustler, and they told me to keep doing what I am doing,” Heeney said. “And I should be fine.”

He has been taking it all in stride the first week of camp, but there is some nervousness.

“The rookies all have to sing a song off the radio in front of the whole team,” Heeney said. “I haven’t been called yet, but I know it’s coming. It’s nerve-racking.”

Legion of Boom II?: The Raiders’ coaches are trying to build up the players’ confidence, and Norton compared the team’s young cornerbacks to the Seahawks’ Legion of Boom secondary.

Norton was on the Seattle staff last year, and said the Seahawks’ nasty defense wasn’t born over night.

“It didn’t start out that way,” he said. “We had to build.”

Norton wants TJ Carrie, Keith McGill and DJ Hayden (15 combined starts) to “bump and run” and “make great plays on the ball.”

“The young corners that I’ve been with in the past, they started out with no one knowing who they were, then all of the sudden, they’re the stars of the league,” Norton said. “And it’s a matter of coaching, developing, time, energy, effort and the whole group. A village raising everybody.”

And he really sees that potential in Carrie, McGill and Hayden?

“Absolutely,” he said. “The talent ... it’s just a matter of work. It’s a matter of experience. It takes time. Winners aren’t built in a week. That’s what camp is for and they’re working their tails off.”

Vic Tafur is a San Francisco Chronicle staff writer. E-mail: vtafur@sfchronicle.com Twitter: @VicTafur