Offensive-minded Bears coach Marc Trestman typically watches an opponent’s defense on film first during the week, but he didn’t have much to say about the Vikings defense during Wednesday’s conference call.

“Tonight is the night I spend more time on that,” the St. Louis Park native said. “I’ve been on the [Vikings’] offensive side of the ball for most of it.”

Facing Vikings running back Adrian Peterson with the worst run defense in the NFL would make any coach shuffle his weekly routine.

The Bears have ranked in the top 10 against the run over the past three years, but this season they are the only team in the NFL to allow more than 140 rushing yards a game (145.2). Their past six opponents have over 100 rushing yards, with two 200-yard rushing games this season. Fresh in Trestman’s mind is Sunday’s 42-21 loss to the Rams, in which three rookies — running backs Zac Stacy and Benny Cunningham and wide receiver Tavon Austin — compiled 261 rushing yards.

Trestman said after reviewing that tape that most of the defensive players did their jobs correctly, but there was always a defender who didn’t spill, or force the runner into the direction of the help side defender.

“We just had guys taking turns missing an assignment even though they were lined up right, they were in the right place and they just didn’t get it done,” Trestman said. “When the offense starts to move and things happen, you’ve got to kind of take the chaos out of it and take your spot and not worry about anything else but filling your spot.”

The Bears have relied on inexperienced players along their front seven because of injuries to linebackers Lance Briggs and D.J. Williams and defensive tackle Henry Melton. Rookies Khaseem Greene and Jon Bostic have filled in as the team’s middle and weakside linebackers, respectively. Nose tackle Stephen Paea also missed Sunday’s game because of a toe injury, and that shuffled the defensive line.

“We’ve got guys that want to help younger guys out; they can’t do that,” Trestman said. “We got younger guys that might want to do more than they have to do because they’re in an on-the-job-training type of environment, and we’ve just got to get all of our guys to just settle down, focus in on their job and do what they have to do on that particular play.”

This all comes after the Vikings had a season-high 232 rushing yards in Sunday’s 26-26 tie with the Packers. Peterson, sidekick Toby Gerhart and the offensive line all looked their best this season. It was a performance the team has expected from the offense all season but, similar to the Chicago defense, the Vikings never seemed to get all on the right page.

“It seems like all year long, it’s one guy here or one guy there that would kill a play,” Gerhart said. “Someone would get beat in this last game, but everyone was assignment-sound, physical and push them off the ball. The running backs put the ball in the right spot and it just worked. It was fun to watch.”

The Vikings offensive line created huge gaps for Peterson and Gerhart, particularly right up the middle, which was one of the Bears’ biggest weak spots Sunday at St. Louis. The Vikings are expecting to see an eight-man box by Chicago on Sunday as Trestman’s way to try to neutralize their matchup advantage.

“It does give you a little bit of confidence going into it when you watch the tape from the week before and you can see another team have success,” Vikings guard Charlie Johnson said. “That, coupled with the success we had last week, we feel like we got a good chance of doing some things.”