The Vikings added much-needed offensive line depth by agreeing to re-sign offensive lineman Joe Berger to a one-year deal, according to an NFL source on Tuesday.

Berger, 31, has spent the past three seasons with the Vikings primarily as a backup guard, but he's made an appearance in every game over the past two seasons. The 10-year veteran started two games last year and nine total during his tenure with the Vikings.

He becomes the team's first offensive lineman signee this offseason. The Vikings return four of their five starters on the offensive line with their only need at left guard. Charlie Johnson, who started at that position last season, is an unrestricted free agent.

If the Vikings don't re-sign Johnson or another guard, Berger would be an option at left guard along with Jeff Baca, whom the team drafted in the sixth round last year.

Cassel admits doubts

Quarterback Matt Cassel returned to Minnesota with a two-year, $10 million deal despite admitting there were moments when he didn't know where he stood with the organization last season.

"As you guys well know, there was always something going on. And you never really knew until Coach [Leslie Frazier] would tell you what's going on," Cassel said. "You just prepare to the best of your ability and you sit there and hope you get a chance to get on the field."

Christian Ponder began last season as the starting quarterback, but Cassel finished the last four games under center. The Vikings went 2-2 to end the season.

"At the end of the day, I was able to get on the field and we were able to finish pretty strong and give myself another opportunity to come back," Cassel said.

Griffen goes golfing

Defensive end Everson Griffen re-signed, getting a five-year deal worth $42.5 million with $20 million guaranteed.

How does one celebrate such a contract? On a golf course.

Griffen was in California last weekend with his agency, Athletes First, for a gala and golf event benefiting Orangewood Children's Foundation.

"I was down there with my friends, other players on different teams, and I was down there just celebrating," Griffen said. "I did a round of golf and was just blessed. I was with my beautiful fiancée, and we were just celebrating and happy and enjoying life."

Griffen wasn't the only Vikings player at the event. Receiver Cordarrelle Patterson, tight end Kyle Rudolph, Cassel and safety Harrison Smith were also there, to name a few.

His golf performance wasn't anything to celebrate, however. Griffen wouldn't disclose what he shot.

"It was not good at all," Griffen said. "I drove the ball a couple of times, but I was just too high on life; just absorbing all of this in."