Center is not the only undecided spot for the Vikings offensive line.

Three weeks before the regular season opener vs. the Saints, the Vikings are testing a couple offensive line combinations featuring guards other than Alex Boone and Joe Berger. During Monday’s practice, Nick Easton and Pat Elflein rotated as the starting center. Another first-team look featured Easton at left guard, Elflein at center and Jeremiah Sirles at right guard.

Offensive coordinator Pat Shurmur was noncommittal when asked if Boone and Berger are locked in as the starting guards. Both have taken the lion’s share of starting reps throughout the summer.

“We’re going to have to see how that all plays out,” Shurmur said. “We’ve got a couple more weeks. We’re going to put the best five guys in there as far as we’re concerned.”

The spark for a potentially new approach appeared to be Friday night’s preseason loss in Seattle, when a starting interior trio of Easton, Elflein and Berger played well, according to coaches.

“I thought it was a better performance, obviously, than [the preseason opener in Buffalo],” Shurmur said. “It was a different scenario. We got a bunch of twists. Those guys were in there playing pretty active. The protections were good. I thought early in the game we ran the ball well.”

Even though Boone missed the exhibition because of an undisclosed injury (his left knee had been wrapped), he still might be hard to displace at left guard. Boone is the second-highest paid offensive lineman on the team with a $6.6 million base salary, $3.4 million of which is fully guaranteed.

So does that put Berger, the 35-year-old veteran on a bargain contract, into a competition at right guard? Coach Mike Zimmer said this spring the Vikings entered the summer undecided at center and right guard. But the latter spot has been controlled by Berger, who has taken nearly every snap there.

“You know, I don’t know. I’m confident it’s my spot and I’m going to keep it there,” Berger said. “But you know, you’re never comfortable. You see a lot of young guys doing a good job in the room and they keep pushing you.”

This time around, those young guys are Easton and Elflein.

Berger, in his 13th preseason, used to be the new guy pushing incumbent starters for their jobs. Now he’s the established one, with 40 starts in the past three seasons for the Vikings, trying to ward off newcomers.

“Yeah I did that a lot of my career, just pushing a guy,” Berger said. “Sometimes I earn the spot, sometimes I help the guy get better.”

Easton, the third-year Harvard product, seems to be the most likely candidate to push Berger for the job at right guard. That is, if Easton isn’t named the starting center over Elflein, the third-round pick from Ohio State.

Easton impressed during his preseason start at guard against the Seahawks, even though he’s spent most of his time at center, including the final five starts last season for the Vikings.

“[Easton] was very active in there. He moved his feet and did a good job of getting to the second level,” Shurmur said. “He did a good job in our screen game, but yet was physical enough to block on the line of scrimmage. He passed off a couple of twists real well. So, all the things you’re looking for.”

The Vikings starting offense scored just three points in Seattle. Still, Elflein drew solid reviews during his start at center, aside from needing “more bass” in his voice to be heard over the crowd at CenturyLink Field.

“We had a few running plays we strung together, which is always good,” Elflein said. “You always have plays that stick out, usually the bad ones. They kind of stay with you. So next game or two you get it corrected.”

All of the offensive line parts, including left tackle Riley Reiff, are expected to finally be available for the Vikings’ third exhibition Sunday against the 49ers. How they’re eventually configured remains to be seen.

“We’ll see what happens,” Elflein said.