NAPA, Calif. -- Sure, the Oakland Raiders have a combined 28 seasons playing inside linebacker in the NFL on the sidelines in general manager Reggie McKenzie, coach Jack Del Rio and defensive coordinator Ken Norton Jr.

But the two guys playing first-team middle linebacker for the Raiders through the first four practices of training camp have a combined zero NFL snaps at the position in practice-squad graduate Tyrell Adams and rookie Marquel Lee.

Zero.

"I guess maybe I can talk Reggie out of retirement," said a chagrined Del Rio after practice on Tuesday. "I don't know."

Del Rio was joking. But his point was clear.

Despite having the reigning NFL defensive player of the year in edge rusher Khalil Mack, a vet presence at outside linebacker in Bruce Irvin, a pair of experienced cornerbacks in David Amerson and Sean Smith and a Pro Bowl free safety in Reggie Nelson, there is a hole in the middle of the defense.

It's a hole that is now being occupied by Lee, the fifth-round draft pick who took over from Adams on Day 3 of camp.

"You work to put a football team together and I think we, in a strong way, addressed a lot of different positions [but] we really haven't attacked [middle linebacker] the same way," Del Rio said. "That's not to say we won't. It's just, you can only do so much each year. It's just the way it's worked out. We've got a collection of young guys right now that are eager, and they're learning. They're developing and we're going to work with these guys and we'll find out.

"We've identified some of [the other positions] and linebacker is also on that list. It's just, maybe it hasn't got checked off the same way other positions have yet."

Into this question steps Lee.

You could say that Lee running with the first-team defense is elevating his game, though he did whiff on stopping running back DeAndre Washington, who threw an epic spin move on him before taking off for a big gain.

"Just having those guys around me, like Khalil and Reggie in the back end, just being around the ones and learning from them, you cannot slack off," Lee said.

"So just elevating my game will have me playing better because I know they've got to count on me to do what I've got to do on the defense and I'm counting on them to do what they've got to do."

Lee said he has been studying the playbook since rookie minicamp and having conversations with the veterans on coverages, as well as talking two or three times a day with Norton. He was asked if he was surprised to be elevated as a starter so soon in camp.

"I wouldn't say it was a surprise, but I wasn't expecting it," Lee said. "I take it along with the challenge, just happy that I've got the opportunity. That's what this game is all about -- opportunity and taking advantage of that. Just coming out and doing the best that I can with the ones."

Especially with Mack in his ear, exhorting him, "C'mon, rook, let's go."

Said Mack: "He's a hell of a player. I can see it already. He has that juice in him, and that's something that I kind of talked to him just to see where his mind is at. We're going to figure out throughout the camp and when we put the pads on, that's when you really get to figure out what type of player you're dealing with."

Then how steep is that learning curve for Lee?

"Well, some guys are natural leaders," Del Rio said. "Some guys are intelligent enough to handle all of that. We'll figure that out as we go through camp. I think he's done a pretty good job thus far of showing that he's a pretty good learner and he's got a good presence about him. We'll see how that grows and whether or not he can earn that. He's going to get every opportunity to compete for it.

"I know that he definitely sees himself as that guy. We like that. It really doesn't matter once you get here how you got here. Whether he's a high pick or a lower pick, he's got a spot here at camp. He's got on opportunity to show us what he's all about. I think he's been pretty solid to start camp."