RENTON, Wash. -- In a move that seemed increasingly likely in recent days, the Seattle Seahawks and All-Pro linebacker Bobby Wagner have agreed to terms on a three-year extension worth $54 million with $40.2 million guaranteed, a source confirmed to ESPN's Adam Schefter.

The deal, which Wagner negotiated himself, makes him the NFL's highest-paid inside linebacker at $18 million per season. As expected, that tops the $17 million average that C.J. Mosley got through the free-agent contract he signed with the New York Jets in March, and it represents a massive jump from the $10.75 million in new-money average from Wagner's 2015 extension.

Wagner was entering the final year of that deal, so his latest extension puts him under contract with Seattle through the 2022 season.

Bleacher Report was first to report the deal, which Seattle announced Friday night.

"We feel blessed that we were able to draft Bobby in 2012, keep him here on a second contract, and now to have him sign a third contract is a huge deal for us," Seahawks general manager John Schneider said in a statement. "Everyone in the whole building is excited, I'm sure his teammates are going to be very excited. He exemplifies everything that we're all about, his professionalism, intensity, the way he handles himself off the field.

"There's no doubt in my mind that he'll go down not only as one of the greatest Seahawks, but also as one of the greatest middle linebackers in NFL history. It's a major deal for our organization moving into the future."

Wagner, who turned 29 in June, has been on a Hall of Fame trajectory. He has made five consecutive Pro Bowls while being named a first-team All-Pro four times in that span. He has topped 100 tackles every season since Seattle drafted him in the second round in 2012, and according to ESPN charting, he leads the NFL in tackles over the past five seasons with 656. Wagner was fourth in tackles last season with 138 while missing only one.

It was thus a virtual certainty that whatever extension Wagner signed would have a higher average than that of Mosley, who has made the Pro Bowl in four of his five seasons but has yet to make All-Pro.

"I'm really excited to have this done, excited that I get to be a Seahawk for a long, long time," Wagner said in a statement. "Like I've always said, I want to play my entire career here, and I feel like today is a step toward that. It feels amazing being here. I've watched people stay, I've watched people go, and to have the trust from the organization to continue to let me lead this team, lead the defense, it's a great feeling. I'm excited to get back to work."

In an Instagram post, Wagner challenged his followers to "dream big and believe in yourself!"

Coach Pete Carroll expressed optimism back in March that a Wagner deal would get done, right after Mosley's deal pushed the presumptive price tag to north of $17 million per season.

"He's never done anything that doesn't represent class and character and leadership," Carroll said of Wagner, a three-time defensive captain, on Thursday. "I'm not even talking about his performance, just the person that he has always been, and he will continue to be that for us. That's just the guy that we know, and we love, and we are happy to have on our club."

Wagner's $18 million average ties him with Tre Flowers of the Detroit Lions for the sixth-highest-paid defender in the NFL, according to Spotrac.

Wagner was previously represented by Athletes First but joined former Seahawks teammates Russell Okung and Richard Sherman in deciding to represent himself. That meant navigating negotiations with general manager John Schneider and VP of football administration Matt Thomas without the buffer and expertise of an agent.

Wagner earlier in the offseason downplayed the difficulty in having direct and blunt conversations with the front office that an agent would otherwise filter when relaying to a player.

"At the end of the day, me representing myself shouldn't be a big deal," Wagner said in May. "They should look at it as any other deal. I think it's a lot of people worried about them saying things and me being able to take criticism. That's part of the game. You've got to be able to take criticism. At the end of the day, you want the person to say something straight to your face how they feel versus to somebody else. I don't need a third party."

Sherman had a celebratory reaction to news of Wagner's deal that also took a shot at the critics of players who represent themselves.

Hell yea!!! Get ya money!!! Who was his agent? https://t.co/EhtaBb0QC3

— Richard Sherman () July 27, 2019

The Seahawks and Wagner had been working toward a deal for a while, and there was a belief within the organization that it would get done early in training camp. Fellow linebacker K.J. Wright, Wagner's closest friend on the team, shared the same belief when he said after the first practice of camp on Thursday that it was his impression that a deal was almost done.

In keeping with the approach he took throughout OTAs and minicamp, Wagner showed up for training camp and attended meetings but was a spectator during practice. Curiously, he watched on Thursday with his sweatshirt turned inside out, showing no team branding. He was back in his No. 54 jersey and Seahawks helmet Friday, even though he again sat out.

Wright was asked Thursday if he sensed any frustration on Wagner's part that a deal hadn't been reached.

"No, I don't think he's frustrated," Wright said. "I believe that something will happen and I'm pretty positive. The organization knows what he means to us and it's kind of, like I said back in OTAs, a no-brainer to get it done."

Said quarterback Russell Wilson on Friday: "He deserves to be the highest-paid linebacker. There's nobody better than him in the game."

Wagner's extension is another major move in what has been an eventful offseason for the Seahawks, who let All-Pro safety Earl Thomas leave in free agency, traded star pass-rusher Frank Clark to Kansas City, and then made Wilson the highest-paid player in league history with a four-year, $140 million extension. Even with Wilson's megadeal, the Seahawks had more than enough cap space to extend Wagner after trading Clark and clearing his $17.128 million in scheduled salary.

"Those are two pillars that we want to build a young football team around," Schneider said of Wilson and Wagner. "That was a primary goal for us as we entered the offseason, and knowing that we're going to be a young football team with great leadership on both sides of the ball -- Bobby, K.J. and Russ -- that's big for us."