HENDERSON, Nev. — Nakobe Dean was signed to be a key piece of the Las Vegas Raiders’ rebuilt defensive core. The veteran linebacker hasn’t been able to show it yet.Dean has been in the Raiders’ building, as confirmed by coaches and evident by his presence at the team’s media day. But the 25-year-old hasn’t been on the field, missing OTAs and mandatory minicamp.Asked whether Dean’s absence has been due to injury, head coach Klint Kubiak neither confirmed nor denied.“Nakobe’s been here every day in practice,” Kubiak said. “But all injuries and things like that, I don’t want to talk about at this time of year. We just want to get all of our guys healthy to training camp. That’s really the most important thing.”Dean signed a three-year, $36 million contract in March, setting up a pairing with fellow free-agent acquisition and former Georgia teammate Quay Walker. Dean was a productive player during his first four seasons with the Philadelphia Eagles, compiling 226 total tackles, 7.5 sacks and 19 tackles for loss. But he also struggled to stay on the field, missing 21 games over the last three seasons due to injury.Assistant head coach Mike McCoy said there’s “no concern” with Dean’s absences. He added that the “No. 1 focus” at this point in the offseason is to “have everybody as fresh as possible and ready to go for the opener.” Walker said it hasn’t been disappointing to not have Dean on the field with him so far, as he’s still present with the team.“You never know what could have happened, or whatever the case may be,” Walker said. “But he’s still here every day. That’s all I can really say as of now.”The Raiders are eager to get Dean back. Linebackers coach Ronell Williams, who came over from Philadelphia with him, described him as a “multiplier” who can establish culture on and off the field. And Walker said his connection with his college teammate can help the duo achieve their best.“We can feed off each other real, real well,” Walker said. “Some days we’re all human, so some days he may come in, he may not be feeling it a little bit, or I may not be feeling it, but we can like feel each other’s energy. We could just pick up and push one another.”Jermod McCoy’s timelineThe only other absence from the Raiders’ two mandatory minicamp practices was Jermod McCoy. The rookie cornerback hasn’t participated in a practice since the team’s first open OTAs session on May 20.A cartilage issue in his right knee is believed to have caused McCoy, viewed as a first-round talent, to fall to the fourth round in April’s NFL Draft. The Raiders have a plan to help McCoy manage his health, spearheaded by wellness coordinator Alex Guerrero, according to Kubiak. The head coach said that McCoy’s absences have been a part of said program.