ALAMEDA, Calif. -- There is no doubt Derrick Johnson has much to prove in what will be his 14th NFL season this fall, his first with the Oakland Raiders.

After all, the Kansas City Chiefs essentially told the longtime fan favorite his services were no longer needed when they exercised the option to void the final year of his contract this spring.

The question, though, is this: How much does Johnson, who turns 36 in November and has torn both Achilles tendons since 2014, have left in the tank?

“The main reason I’m still playing ball and chasing a championship ring [is] just because I believe I have a lot left in the tank; I have a lot left in the tank,” Johnson, who signed with Oakland on May 7, emphasized on a recent conference call with Bay Area reporters. “That’s the only reason I’m back. When I get to a point where I’m like, ‘Man, I’m hanging on,’ I’ll get out. I’ll get out of the NFL.”

Indeed, Raiders coach Jon Gruden believes there is enough playmaking ability remaining in Johnson to have him serve as Oakland’s middle linebacker in a rebuilt 4-3 base defense. Yes, that means purportedly taking the place of NaVorro Bowman, who is more than five years younger but also has had major injuries to his left knee and left Achilles (Johnson was Pro Football Focus’ 33rd-ranked linebacker last season with an overall 77.3 grade, while Bowman was 11th with an 84.8 grade).

Derrick Johnson, who'll turn 36 in November, is Kansas City's all-time leading tackler. Kirby Lee/USA TODAY Sports

Coming from the Chiefs also should help stoke this ancient AFC West rivalry, what with Johnson’s standing as Kansas City’s all-time leading tackler with 1,262 stops and a four-time Pro Bowler with 27.5 career sacks, 23 forced fumbles, eight fumble recoveries and 14 interceptions.

“He brings us status at a critical position,” Gruden said. “He’s got a great history in this league. He’s been productive under a lot of different coaches, different schemes. He understands the AFC West. He certainly understands this rivalry. I’m really excited to add him to our team with Tahir Whitehead and some of our young linebackers. I think his presence will be very valuable.

“Getting a guy like Derrick Johnson, I think, could be huge for us.”

Again, so long as the 6-foot-3, 242-pounder is healthy, right?

Johnson blew out his right Achilles tendon in the 2014 season opener and was back for a full 16-game season and Pro Bowl nod in 2015. He tore the left Achilles in Week 14 of the 2016 season, against the Raiders. He played in 15 games last year.

And as Johnson said, it takes nearly two years after an Achilles tear for a player to feel as he did before the injury, so he is in that sweet spot for Oakland, so to speak.

“My burst is back -- it’s better than ever and it’s a good feeling because it’s going to help me make plays, it’s going to help me be explosive, and the longer you’re out from your season-ending injury, it usually gets better and it helps you out mentally,” Johnson said. “This will be my second season out from my last Achilles injury. I was healthy last year. I’m even better this year because I got a really good offseason training that I really didn’t get to do last year because I was coming off of the injury.

“But, man, I’m excited, my body is healthy. At this age, being healthy is big. That’s one of my goals -- if I can be healthy, I can help this team win -- be an impact player.”

And still ...

“Sometimes [that type of injury] is hard to quantify because it may be more of a feel for them,” said ESPN injury analyst Stephania Bell. “Things like getting off the line of scrimmage, making sharp cuts, getting vertical in a hurry. But they simply have the sense that these things are coming easier.

“Obviously, at 36, performance metrics tend to be in decline, for most, so the question is really a) can the athlete get back to pre-injury level? and b) is he healthy enough to maintain that performance level? Sometimes athletes will surprise and bump back up in their metrics at two years post-Achilles. Sometimes they were having trouble with the Achilles before it ruptured, which could have impacted their metrics pre-injury to a degree.”

Which brings it all back to Gruden and his recruitment pitch to Johnson when he visited the Raiders nearly two weeks ago.

Gruden had a specific plan in mind for Johnson and his playing time, one that neither coach nor player would give specifics on. But given Johnson’s take on it -- “Oakland had the best plan for me at my age that I’m at now,” Johnson said -- and his skill set at such an advanced NFL age -- Johnson is actually better against the pass than against the run, as evidenced by his ranking seventh at linebacker in the NFL with a PFF coverage grade of 86.0 -- it’s easy to surmise what said plan entails.

Even if he claims to still be a three-down linebacker.

Jon Gruden has embraced taking older, veteran players. AP Photo/Jeff Chiu

“The plan is evolving,” Johnson said. “The plan is a full ... process kind of deal, so I’m at the beginning of it.

“At my age, you have to be more specific as far as game planning and actually being a part of winning ... and Jon Gruden, his tenacity and intense motivation. His mental aspect of the game is off the roof. When he told me about that plan and he told me about the plan he had for me, I had to jump on it. I had to jump on it.”

Gruden, in his second tour with Oakland, is following a similar script he had in 1998, when he sprinkled several veterans on the roster. Think Anthony Newman, Richard Harvey and Eric Allen. This offseason, the Raiders signed eight players who are at least 30 years old, including quarterback Josh Johnson, who was released on Thursday.

What’s that about a plan again?

“It’s a 4-3 scheme, a linebacker-friendly scheme,” Johnson said. “It’s a scheme that’s built for linebackers to make plays. We have a lot of responsibility in this defense. With my wisdom from playing for 13 years ... they ask the linebackers to do a lot mentally, just so we can make plays, and that is right up my alley.”

The Raiders certainly believe so. Which is why the likes of quarterback Derek Carr and running back Marshawn Lynch made a point to make Johnson feel at home in offseason workouts.

Even if, yes, the Chiefs' defense has owned Carr (he is just 2-6 against Kansas City) and Lynch is relatively new to the rivalry.

“[Carr] already said, ‘I hated when you did this’ or ‘I thought you were going to do this and you were just playing mind games with me.’ So, it was a pretty cool deal,” Johnson said.

And Lynch?

“Finally, we link up, baby,” he told Johnson. “We’re linked up to try to get this thing done.”

“I expressed this to Coach Gruden: I wasn’t interested in some type of rebuilding atmosphere,” Johnson said. “As soon as I said that, he had that look in his eye like, 'You’re talking about the sense of urgency to win.' That’s exactly right. As soon as he said that, I said, ‘Yes, that’s what I want.’ My timing, I want to win now. We’re on the same page as that.”

Sounds like a plan.