Joe Berger was in the U.S. Bank Stadium locker room saying not to read too much into what certainly appeared to be a significant development in his competition with John Sullivan for the Vikings' starting center position.

"I'm trying not to think about it too much," said Berger, who played the entire first half while Sullivan was a healthy scratch in Sunday's 23-10 preseason victory over San Diego. "We'll know in the next few days how it's going to settle up."

Meanwhile, one room over, coach Mike Zimmer also was tapping the brakes on the growing urge to assume the popular Sullivan's days with the team that drafted him in 2008 are numbered.

"[Playing Berger] was really more of a thing that we've [already] seen Sullivan in two preseason games," Zimmer said. "Berger hadn't played center in [the preseason]. We hadn't seen that combination with him and [right guard Brandon] Fusco. So that's really what it was."

Of course, the Vikings hadn't seen Sullivan and Fusco together either. Berger played right guard for the injured Fusco in the first two preseason games. The Vikings also chose not to rotate first-team centers in the first half Sunday as they had done in practice two days earlier.

With time to decide on a starting offensive line unit running out, Sunday's game was the most significant test to date for the team's No. 1 offseason priority. That's often the case for a third preseason game since many starters typically are rested in the final exhibition.

Berger

If that's the case, then Berger stated his case rather well starting with the second snap of the game. Berger snapped the ball, got the jump and leverage on 333-pound nose tackle Ryan Carrethers and, well, we'll let him describe it.

"I'm just manned up with the nose, and I'm just driving him," Berger said. "That's how you draw it up."

Berger drove Carrethers to the right, creating a big hole and setting the stage for fullback Zach Line to slide left and, well, we'll let him describe it.

"I try to slide behind the lineman without touching them because it could knock them off their block," Line said. "Then I find my linebacker in the hole and hit him. That was exactly the look we wanted."

With Line ousting Manti Te'o, ball carrier Jerick McKinnon came through so clean that he, well, we'll let him describe it.

"I didn't even get touched by a fly," said McKinnon, who ran 30 yards before any contact was made on the 35-yard run.

The Vikings had struggled to run the ball in the first two preseason games, averaging 2.5 yards on 51 carries. Granted, Berger was at left guard for parts of those games. And we'll never know what would have happened Sunday if Sullivan had started.

But with Berger and Fusco together for the entire first half, the Vikings averaged 6.1 yards on 13 carries and completed 12 of 16 passes for 161 yards and a 127.3 passer rating. Throw out the nifty 22-yard scramble for Teddy Bridgewater, and the average is still 4.8.

"We really didn't run the ball that well the first two preseason games as a starting offense," tight end Kyle Rudolph said. "Everybody knows that's our identity. You saw a lot of stuff we practiced all week carry over to [Sunday]."

Sullivan, who had left the locker room before reporters arrived, started 96 of 113 games after taking over for Matt Birk. But he missed all of last season because of two back surgeries. He's also 31 and doesn't have position flexibility, whereas the 34-year-old Berger has started and performed at a high level at center and both guard positions.

Ideally, you'd want Sullivan to beat out Berger, who would then back up three spots. But Berger isn't backing down a year after Pro Football Focus ranked him first among all NFL centers while subbing for Sullivan.

"I guess it's a good problem to have because they're both great centers," Fusco said. "You just wonder how it's all going to shake out. It's tough. They're best of friends. But it's part of the business."

Mark Craig covers the Vikings and the NFL for the Star Tribune mcraig@startribune.com