When the media walked through the chain-link fence down to the practice fields at Winter Park on Monday morning, eyes immediately fixated on the front line of the team stretch, where the big offensive linemen usually choose to get limber.

Reporters scanned through the numbers in 60s and 70s. Once again, there was no 65.

Center John Sullivan has not been spotted on the practice fields there, or on any other football field for that matter, for three weeks. He has missed 11 consecutive practices and a trio of preseason games since his “back spasms,” as the team has called it, flared up on Aug. 18.

The Vikings kick off their regular season in six days, against the 49ers on Monday night.

Their offensive line was arguably their biggest question mark even before the steady center, who has started 57 consecutive games, got lost in the trainer’s room. And now, with each day and each practice that passes by, it looks more and more likely that the Vikings will be without the anchor of their new-look offensive line in Week 1.

Coach Mike Zimmer was noncommittal Monday about Sullivan’s status for the season opener. However, he insisted again that he still isn’t overly concerned.

“Not really,” Zimmer said. “He’s getting better every day, so we expect we might get him out here a little [Tuesday]. We’ll see.”

The Vikings, both publicly and privately, have downplayed the injury since Sullivan first missed practice three days after starting against the Tampa Bay Buccaneers in the second preseason game.

Asked Monday if the team had anticipated Sullivan to be sidelined this long, Zimmer responded, “You never know. But he’s getting better every day, so I’m encouraged.”

Adding to the mystery of Sullivan’s absence is that he hasn’t even left the building to watch practice once over the past three weeks. Meanwhile, cornerback Josh Robinson and nose tackle Shamar Stephen, two other players who have been out of commission for weeks, usually tug on a jersey and purple shorts and walk out to watch practice from the sidelines.

On Monday, with Sullivan nowhere to be seen, trusty veteran backup Joe Berger, whom the Vikings prioritized re-signing in free agency this past offseason, again lined up in his place. Zac Kerin, a second-year lineman, continued to practice as the second-team center.

If Sullivan isn’t able to play against the 49ers, Berger would get the start.

Berger, the team’s top interior reserve, filled in for Sullivan once last season when Sullivan got knocked out of the Week 7 loss to the Bills because of a concussion. He also started 11 games at guard the past two seasons. While the Vikings view him as a backup, there is a comfort level with him in there.

“He’s doing good,” Zimmer said of Berger. “These guys all get paid a lot of money to do this, so we expect all these guys when they get in there to [perform].”

Berger, who also is experienced when it comes to the media game, laughed off a question about whether he will start against the 49ers. He did say he would be ready if his number is called.

“Of course,” said Berger, who started two preseason games with Sullivan out. “That’s why I’m here. Obviously, we all want the starting five out there. If they can’t be for some reason, that’s why I’m here.”

The Vikings have question marks at the four other offensive line positions, too.

Matt Kalil was one of the NFL’s leakiest left tackles a season ago, though Zimmer believes “Kalil’s had a really good preseason.” Left guard Brandon Fusco is manning a new side on the line, and the Vikings moved lifelong tackle Mike Harris inside to replace him at right guard. Fourth-round pick T.J. Clemmings will start at right tackle.

But whether it is a rookie tackle or Berger potentially stepping in for Sullivan, the Vikings are counting on someone to keep defenders off quarterback Teddy Bridgewater and running back Adrian Peterson.

“It happens every year in this league — guys step up and do good,” Zimmer said. “So that’s what our expectation is.”