MINNEAPOLIS — The Minnesota Vikings have found some feistiness and experience for their unsettled offensive line, a step toward galvanizing a position group that has been lagging the past three years.

Former San Francisco 49ers left guard Alex Boone agreed Wednesday to a four-year contract, according to a person with direct knowledge of the deal. The person spoke to The Associated Press on condition of anonymity because the Vikings had not yet announced the signing.

The 6-foot-8, 300-pound Boone, who begins his eighth season in the NFL, meets the top offseason need for a team that has struggled to protect quarterback Teddy Bridgewater in his first two years in the league.

Adrian Peterson was the NFL rushing leader last season, but the running game didn’t dominate as it did in 2012 when Peterson was the league MVP with 2,097 yards.

The Vikings didn’t spend a bunch of money or make the big splash on the first day of NFL free agency, but they were plenty busy upgrading a team that won the NFC North division with an 11-5 record in coach Mike Zimmer’s second season.

They re-signed one of their free agent offensive linemen, right guard Mike Harris, to maintain some depth. They worked on the defense, too, highlighted by the snag of veteran safety Michael Griffin, who has played the past nine seasons with the Tennessee Titans.

Griffin agreed to a one-year contract, according to a person with direct knowledge of the deal, who spoke on condition of anonymity to the AP because the team had not yet announced the signing.

Griffin was released last month by the Titans, who drafted him in the first round in 2007. He’s a two-time Pro Bowl pick who had one of his 25 career interceptions last season.

The Vikings also finalized a one-year contract with backup defensive tackle Kenrick Ellis, who joined the team midseason after being let go by the New York Giants. Ellis is in his sixth year in the NFL after being drafted by the Jets in the third round in 2011. They reached reported agreements with linebackers Emmanuel Lamur (Cincinnati Bengals) and Travis Lewis (Detroit Lions), too.

The focus was the offensive line, though, as it will be all season.

Harris, a fifth-year veteran, played relatively well at his new position in 2015 after serving as the primary backup tackle the season before, so he’ll likely compete with Brandon Fusco for a starting spot.

Fusco, who was recovering from a torn pectoral muscle that limited him to three games in 2014, didn’t make a smooth transition to left guard last year.

The Vikings kept left tackle Matt Kalil, guaranteeing his $11.096 million salary for 2016, after bringing back right tackle Phil Loadholt at a reduced rate.

Center John Sullivan, who like Loadholt missed the entire 2015 season because of injury, will return in an attempt to re-establish himself as a reliable anchor. His versatile replacement, Joe Berger, performed remarkably well, one bright spot on a front that was forced to start rookie T.J. Clemmings in Loadholt’s place.

So the questions will remain until the games begin in September, but for now the addition of Boone has at least quelled some anxiety within the fan base.

Boone switched from the right side to the left side last season, when new Vikings offensive line coach Tony Sparano supervised San Francisco’s tight ends. Boone was on the 49ers practice squad in 2009, made the active roster the following year and became a starter in 2012 on San Francisco’s NFC championship team.

Boone, undrafted out of Ohio State in 2009 in part because of some off-field trouble related to alcohol abuse he sought counseling for, has long played with a mean streak.

He infamously said he’d like to punch Clay Matthews in the face after the Green Bay Packers linebacker levied an illegal hit on 49ers quarterback Colin Kaepernick in 2013.

Last season, Boone was accused by New York Giants linebacker Jon Beason of grabbing him from behind and pushing him in the back before a crown-of-the-helmet contact by 49ers running back Carlos Hyde caused Beason’s concussion.