Injuries to Sullivan, Floyd are a test to Vikings' depth

Roster depth has been a strength during a seven-week start that has seen the Vikings go 4-2 while clinging to the sixth seed in the NFC playoff race.

Monday, coach Mike Zimmer indicated his team might have to lean on that depth at center for the rest of the season and at defensive tackle for at least the near future.

Center John Sullivan, who was eligible to return from injured reserve in Week 9, re-injured his back lifting weights 10 days ago and had a second surgery, Zimmer said. Zimmer called Sullivan's chances of returning this season "minimal." Per NFL rules, the Vikings can't shift the designated IR return from Sullivan to another player.

Meanwhile, an NFL source said defensive tackle Sharrif Floyd had knee surgery to remove cartilage and that his return date is uncertain. Floyd finished the Chiefs game two weeks ago, but missed all of practice last week and Sunday's victory at Detroit after being listed on the injury report with knee and ankle injuries.

Floyd was wearing a walking boot on his left foot in the locker room during Monday's media access period. He wouldn't give specifics on his injury.

"I felt like I was gimpy, but obviously that wasn't the case and it came out a little [more serious] than I thought," the 2013 first-round draft pick said. "Hard to swallow, but that's just how it came up."

Later, Zimmer was asked if the foot was broken. He said, "He had a little piece of cartilage taken out." The NFL source said the cartilage was taken from the knee, not the ankle.

"I've heard all kinds of ranges," Zimmer said.

As for Sullivan, the Vikings were expecting their best offensive lineman to return and bolster not only the center position, but the protection communication that has lacked consistency with Joe Berger starting the first six games.

"It was disappointing," Zimmer said of Sullivan's setback. "He was doing really, really good and then all of a sudden had a little mishap.

"As far as Joe specifically, I thought he's done a good job. He's getting guys for the most part in the right place. We've had a few mishaps here and there when we've had the wrong assignments. But overall he's done a good job."

Meanwhile, without Floyd, the Vikings leaned heavily on inside nickel pass rusher Tom Johnson and nose tackle Linval Joseph to play more snaps. Johnson started in place of Joseph, and both of them played 44 of the team's 54 snaps.

"Tom did a good job," Zimmer said. "He's a veteran guy who knows what we're trying to get done."

Johnson had one of the team's seven sacks and was a key defender during a goal-line stand that saw the Vikings stop the Lions four times from the 1-yard line.

The Vikings held the Lions to 19 points, giving them a safety for strategic reasons in the closing seconds. The defense is now tied with Denver for No. 2 in points allowed (17.0). Only Green Bay ranks higher (16.8).

After the Lions produced 155 yards and two touchdowns in their first two possessions, the Vikings held them to 9 yards of offense in their next seven possessions. A day later, the Lions fired offensive coordinator Joe Lombardi and offensive line coaches Jeremiah Washburn and Terry Heffernan.

Now, the Vikings travel to Chicago, where they haven't won since 2007. Only three players on the current roster — Adrian Peterson, Chad Greenway and Brian Robison — are left from that team.

When the subject of the team's losing streak in Chicago was mentioned Monday, Zimmer said, "I was hoping you'd bring that up."

He was smiling.

"I like proving people wrong," he said. "People have doubted me for a long, long time. I hope they keep doubting our football team, because that's the mentality I'm trying to get them [to have. Say what you want and let's go prove it."

So who's doubting the 4-2 Vikings?

"There was a lot of doubters after we lost to San Francisco, right?" he said. "I don't know. When people say we lose all of these games, we can't win a game on the road, we can't win a game in the division, I just take it personally, I guess."