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 on 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 in Seattle through the 2022 season.

Bleacher Report was first to report the deal.

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.

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.

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 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.