With Vikings center John Sullivan out for at least eight weeks after back surgery, the team is now going to rely on versatile offensive lineman Joe Berger to step in and perform the gigantic task of trying to replace one of the best centers in the NFL.

The loss of the former sixth-round draft choice out of Notre Dame in 2008 is a big blow. Berger, who was a sixth-round pick by the Carolina Panthers out of Michigan Tech in 2005, has started 38 games entering his 11th year in the NFL, and last season he started nine games at right guard when Brandon Fusco went out because of a torn pectoral muscle. This will be a different experience for Berger, but he believes he's ready.

"It's different stepping in there at center when I'm used to playing guard," he said. "Sully does a lot for the guys as far as [blocking-scheme] calls and stuff like that, so trying to fill that spot, there's big shoes to fill."

Berger has played some center during the preseason and he talked about the nature of switching positions along the offensive line.

"When you get used to one spot, it's a little difficult to switch," he said. "It takes a little bit to get used to the technique differences. I think guard and center are different in that guard is a little more physical and center is a little more mental."

No limitations

Offensive coordinator Norv Turner talked this week about how offensive linemen have to be able to move from position to position. That versatility will be tested early this season.

Minnesota Vikings guard Joe Berger (61)

"There are no limitations," Turner said. "We're asking a lot of those guys, as I've said. I think we've gotten better, a lot better, on the left side. Those guys [Fusco, who moved from right guard to left guard, and tackle Matt Kalil] are veteran guys, they're comfortable with each other. I think we've improved on our left side. We're making progress every day on the right side.

"Obviously we have a position-change guy [Mike Harris going from tackle to right guard] and a young guy [rookie right tackle T.J. Clemmings], but they've responded. We did a good job of protecting the quarterback in the preseason, we need to continue to do that and be able to run the ball."

Berger knows this is why he has been with the Vikings for four years — to be able to play anywhere when someone gets injured — but this might be his biggest test.

"That has been kind of my role here … be the next guy in," he said. "I have taken pride in the fact that when someone goes down in any of the three spots, I can come in and play close to their level."

One reason Berger says he is ready is because he spends time in practice each week moving from position to position with the first-team offense.

"Depending on what the plan is for the week — in the season when I'm the backup for all three, we just roll through different spots throughout the week and get used to playing with the starters at each spot," he said. "In the practices, [I'll take] quite a few [snaps]; in each period, I'll take one at each spot. That adds up to 20, 30 reps in practice."

One of the small benefits to Berger is that, in this situation, he has had time to prepare for replacing a player, compared to an in-game injury. But he described what that moment is like for a backup.

"You just have to go," he said. "You have to go in, make it work for that series. When you get to the sidelines and the defense is out there, you take a minute to collect your thoughts and be ready to go and finish the game up."

While some players like to say everything comes easy, Berger was honest when asked if it's difficult to move from position to position at the NFL level.

"It is. You have to spend a lot of time, you have to get good at taking reps when you're sitting back and watching the starters practice," he said.

Berger knows he will be the starter for at least half the season. If the Vikings are going to have any success, they're going to need Berger to fill in as well at center as he has at other positions throughout his career.

Biggest win over 49ers

The Vikings probably scored their most impressive victory over San Francisco in the playoffs following the 1987 season when they defeated the 49ers 36-24 after leading 20-3 at halftime at Candlestick Park. That was a 49ers squad that included quarterback Joe Montana, wide receiver Jerry Rice and running back Roger Craig. They had been favored to beat the Vikings by 11 points.

San Francisco had gone 13-2 in the regular season, and the Vikings had finished 8-7 during a strike-shortened season. The Vikings were coming off a surprising 44-10 wild-card playoff victory over New Orleans at the Superdome.

Jerry Burns was Vikings head coach at the time and he remembers what a great day Vikings quarterback Wade Wilson had (20-for-34 passing for 298 yards, two touchdowns and one interception), throwing especially to Anthony Carter, who had 10 receptions for 227 yards.

"We just were hot and played by far the best game we played all year," Burns said.

The underdog Vikings finished with 397 total yards compared to the 49ers' 358 yards, and they also picked off Montana and Steve Young once apiece. The Vikings came within one reception of going to the Super Bowl when they lost 17-10 to Washington in the NFC Championship Game. The 49ers would go on to win Super Bowl XXIII following the 1988 season after suffering one of the biggest upsets in franchise history.

Gophers line OK

Right tackle Josh Campion, the Gophers' top offensive lineman who missed the TCU game, said his concussion symptoms hit him in practice last week. However, he said Thursday he is 100 percent healthy and will be ready to start Saturday at Colorado State.

The offensive line that will open against the Rams will have Jonah Pirsig at left tackle with Ben Lauer, who started against TCU, in reserve.

Colorado State quarterback Nick Stevens was named the Mountain West Offensive Player of the Week after going 20-for-28 for 289 yards and five touchdowns in a 65-13 opening rout over Savannah State.

Jottings

• In three career games against the 49ers, Vikings running back Adrian Peterson has gained a total of 174 yards on 58 carries (a 3.0 average). But the word is that this 49ers defense is not as good as the one they had last year, when they ranked fifth overall in the NFL.

• 49ers GM Trent Baalke was an All-North Central Conference football player when he played outside linebacker at Bemidji State from 1982-1986.

• Three 49ers assistant coaches spent time coaching with the Gophers. Scott Brown was defensive line coach from 1992-1994 and linebacker coach in 1995. Offensive line coach Chris Foerster was on the Gophers staff in 1992, and also was a Vikings assistant from 1993-1995. Special teams assistant Richard Hightower was on the Gophers staff as a wide receivers coach in 2009.

Sid Hartman can be heard weekdays on 830-AM at 7:40 and 8:40 a.m. and on Sundays at 9:30 a.m. shartman@startribune.com