The Vikings started the season with four defensive linemen entering the final year of their contracts. They reduced that number by one on Wednesday, signing defensive end Brian Robison to a four-year contract extension.

The deal is worth $28.3 million, including $12.1 million in guaranteed money with a $5 million signing bonus, and presumably will enable the 30-year-old Robison to finish his career in Minnesota. Robison had a chance to become a free agent after the season but elected to remain with the team that drafted him in 2007.

"I think in any player's mind, anytime you have an opportunity to hit free agency, it creates a little bit of excitement," Robison said. "But after me and my family sat down and talked about things, we realize there's not a whole lot of guys in the league that get to start their career in one place and end their career in one place. This is an opportunity for me to do that."

Robison became a full-time starter in 2011 after the team signed him to a three-year, $14.1 million deal. He has proved to be a reliable every-down player.

"That deal, to me, was an opportunity to be a starter and opportunity to prove myself in this league," he said. "I was able to do that. I'm not going to sit here and toot my horn. I'm just very thankful to the Vikings for giving me that opportunity."

Robison's signing gives the Vikings some stability at that position as they look to the future. Jared Allen, Kevin Williams and Everson Griffen are scheduled to become free agents at season's end.

Brian Robison struck a four-year, $28.3 million deal with the Vikings that will give the defensive end $12.1 million in guaranteed money.

"A number of our guys are going to be out of contract at the end of the season so to have Brian under contract, that's very important going forward and we're pleased that has happened and hopefully we'll get some of the other guys taken care of as well," coach Leslie Frazier said.

No changes in secondary

Frazier said he's not making any personnel changes in the secondary, which means struggling cornerback Josh Robinson will remain a starter for Sunday's game against Carolina.

"Having Chris Cook and Jamarca [Sanford] back, that will be the biggest change, having those guys back," Frazier said. "That will help us."

Both cornerback Cook (groin) and safety Sanford (hamstring) missed the Pittsburgh game Sept. 29, but the team is hopeful that both will be able play Sunday.

Frazier indicated before the bye week that the coaching staff would consider making changes, but it decided to keep Robinson as the starter on the left side, rather than elevate rookie Xavier Rhodes.

According to Pro Football Focus, Robinson has given up 35 completions on 38 targeted passes for 391 yards. Frazier acknowledged that Robinson has struggled this season, especially in the slot/nickel role, but the coaching has resisted replacing him with Rhodes in the starting lineup.

Frazier said he prefers to keep Rhodes as the third cornerback who plays on the left side in the nickel package.

Friendly foes

Frazier and Carolina coach Ron Rivera are longtime friends who still talk at least once a week. The two were teammates in Chicago when the Bears won the Super Bowl following the 1985 season. They also served as assistant coaches in Philadelphia from 1999 to 2002.

The two friends have had plenty to discuss with both of their teams off to 1-3 starts.

"During this early stretch of the season we've tried to pick each other up at times," Frazier said. "We usually talk at least once a week during the season and in the offseason as well. I just try to encourage him as best I can and share some insight from my perspective, and he does the same with me. He'll share some things with how he's doing things or how things are done where he is and whatever he thinks might be able to help me."

Roster moves

Quarterback McLeod Bethel-Thompson, waived Monday to make room for Josh Freeman, was claimed off waivers by the San Francisco 49ers. The Vikings were hoping Bethel-Thompson would clear waivers so they could sign him to the practice squad.

The Vikings also waived defensive end George Johnson and claimed defensive end Justin Trattou, who played five games as a special teamer for the New York Giants this season before being waived.