Having called offensive plays in the NFL since before some of his players, including his starting quarterback and running back, were born, Norv Turner knows the drill.

Some weeks — throughout Turner’s career, more often than not — seemingly every “go route” you scribble onto the chalkboard is seen as a stroke of genius.

Other weeks, when things aren’t going well, every talk radio caller or die-hard with a Twitter account thinks they can draw up better plays from their sofas.

“Anyone who has coached a limited time or a long time in this league knows this is a week-to-week league, and every week presents a whole new set of circumstances, a whole new challenge,” Turner said Thursday. “That’s why from my standpoint you never get too high or too low, and that’s why you try to teach that to your football team.”

Pretty much anything is possible in this league, including losing four offensive starters and a key reserve before the fourth game of the season. But it’s hard to imagine the Vikings offense getting much lower right now as it awaits another tough test against the Buffalo Bills on Sunday.

In their past two games, the Vikings have scored only 13 points. Their quarterbacks have been sacked 14 times and thrown five interceptions. Their top two wide receivers have been nonfactors. They are not getting much production from their tight ends. And they decided to make a change at running back after another week of 3-yard gains and a cloud of punts.

As a result, the Vikings have plummeted to tied for 28th in the league in scoring (17.3) and now rank 27th in total offense (314.7 yards per game) through Week 6 — and that’s including a 41-point, 558-yard performance against the Atlanta Falcons only three weeks ago.

The offense’s decline prompted coach Mike Zimmer to defend Turner earlier this week.

“I have 100 percent confidence in Norv Turner and the offensive staff,” Zimmer said.

Meanwhile, Turner’s players have been taking turns shouldering the blame.

Quarterback Teddy Bridgewater says he can make quicker decisions in the pocket. Cordarrelle Patterson says he feels he and his fellow wide receivers are letting their quarterback down. New starting running back Jerick McKinnon says he believes a more consistent running game would ease Bridgewater’s burden. And one can assume that the veteran leaders on the embattled offensive line, if they ever entered the locker room when it was open to media, would say they must block better, too.

Turner said his players can’t sit around feeling sorry for themselves. They have to overcome the stalled drives and negative plays and find a way to capitalize on the next opportunity.

“We need to get the ball completed to all of our guys, we need to get better in the running game obviously, we need to manage the game as well as we can,” Turner said. “Again, when you’re struggling a little bit, you can withdraw a little bit. We can’t withdraw. We’ve got to be aggressive. We’ve got to go.”

And that includes Bridgewater. Turner said the rookie played tentatively after throwing a red-zone interception on the team’s first drive in last week’s 17-3 loss to the Detroit Lions.

“I think after you do that, you can be a little bit too careful, you can make sure on some throws,” Turner said. “And I think there were a number of throws where it wasn’t about his release [time], it was about anticipation and trusting what you see and turn the ball loose.”

Bridgewater — who played well against the Falcons in his first NFL start, then threw three interceptions against the Lions in his second — is still looking for the first touchdown pass of his career. Matt Cassel threw the team’s most recent touchdown pass, way back in Week 2.

“I wouldn’t say I remember having gone that many [games] without a passing touchdown,” Turner said.

While Turner isn’t one to make excuses, he certainly wasn’t imagining Bridgewater faking a handoff to McKinnon before deciding whether to throw to tight end Chase Ford or wide receiver Jarius Wright when he was drawing up the Vikings offense before the season.

No, his offense was built around Adrian Peterson, with play-action passes potentially going to emerging tight end Kyle Rudolph or Jerome Simpson, the team’s only true deep threat. He also was probably counting on a sturdier offensive line with Brandon Fusco at right guard.

“I think you saw it in the [St. Louis] Rams game that there are things that looked like they were going to be really exciting,” Turner said. “When you have the ability to run the ball and the threat to run the ball, it helps a quarterback. It certainly helps a young quarterback, but we know where we’re at, and we’ve got to make this thing go.”

The Vikings are down right now, but they still believe Turner is the kind of offensive genius who can help them break out of this funk.

“We have a ton of confidence in Coach Turner. He’s one of the best offensive coordinators in the game,” Bridgewater said. “We’re just going to continue to find different ways to get our playmakers the ball. Just want to get back to winning form.”