Harrison Smith, fresh off his first Pro Bowl season, is one of the NFL's best safeties. On Monday morning, the Vikings agreed to start paying him like one.

The Vikings signed Smith, who would have been an unrestricted free agent after the 2016 season, to a $51.25 million contract extension that will keep the versatile playmaker under team control through the 2021 season. The five-year extension includes $28.578 million guaranteed, according to a league source.

At $10.25 million per season, the new contract makes Smith the NFL's highest-paid safety, according to OverTheCap.com. His deal topped Earl Thomas of the Seattle Seahawks, who signed a four-year, $40 million extension two years ago.

Smith sat down with General Manager Rick Spielman before 8 a.m. to sign the contract, then immediately celebrated by walking downstairs to attend a team meeting.

"It's very hard to put into words right now," Smith told the team's website. "Coming into the league, getting an opportunity after getting drafted by Rick and being able to stay around here and just be a part of what we're building here, what Coach [Mike] Zimmer is building … It's huge in every type of way I can think of, being able to stay in this building and chase a championship."

Smith, who will have a news conference Tuesday, was a first-round draft pick of the Vikings in 2012. Now in his fifth season with the organization, the 27-year-old has thrived the past two years under Zimmer, who uses Smith in a variety of ways to put stress on offenses.

Smith played in his first Pro Bowl, albeit as an injury replacement, this winter after recording 66 tackles, 1.5 sacks and a pair of interceptions in 13 games in 2015. He ran back one of those interceptions for a touchdown in Week 16, giving him four career interceptions returned for a touchdown, a franchise record.

In his first four NFL seasons, Smith racked up 320 tackles, 5½ sacks and a dozen interceptions. Willing to hit hard, he has also forced three fumbles.

Since 2012, Smith is the only NFL defender to record at least 300 tackles, five sacks and 10 interceptions and return at least four interceptions for scores.

Shortly after the 2015 season ended, Spielman expressed a desire to extend Smith's contract this offseason, playfully joking that Smith was one of the "better," not best, defensive playmakers in the NFL in the hopes of keeping his price down.

Smith, meanwhile, continued to express confidence a deal would get done, pointing to Spielman's track record of rewarding homegrown talent.

Entering the process, Smith made it clear he wanted to be the NFL's highest-paid safety. The Vikings and his agent, Brian Murphy of Athletes First, remained in touch throughout the spring. And after exchanging numbers multiple times the two parties agreed to a deal that satisfied Smith's financial demands while still making the Vikings feel comfortable.

The Smith signing continues a trend for Spielman and top contract negotiator Rob Brzezinski, who aimed to get young players who they feel are still ascending under contract before they reach free agency. Those players have included guard Brandon Fusco, tight end Kyle Rudolph and kicker Blair Walsh.

Next offseason, the Vikings must turn their attention to cornerback Xavier Rhodes and possibly defensive tackle Sharrif Floyd, who were first-round picks in 2013 and are under contract though the 2017 season. After that will come quarterback Teddy Bridgewater and outside linebacker Anthony Barr.

Keeping Smith long-term was one of the team's top priorities this spring. But Smith wanted to stay with the Vikings, so it was only a matter of time until a deal got done.

"With the fans in Minneapolis, I couldn't imagine a better place to play and a better organization to be a part of," the 6-2, 214-pound safety told vikings.com. "I just can't say enough about how blessed I am to stay here."