– With all due respect to quarterbacks and cornerbacks, offensive linemen might be the most pivotal players in an era that only shows signs of elevating last year’s average of 70.9 passes per NFL game.

At least that’s how Vikings offensive coordinator Norv Turner is starting to see things in his 30th NFL season.

“It’s becoming the hardest place in the league to play because, obviously, the pass rushes have become such a big deal,” Turner said. “The variety of schemes you see [have increased], so that group really has to work together.”

As rain fell Sunday, the Vikings still went outdoors in full pads for the first time since Mike Zimmer became head coach six months ago. Naturally, most eyes remained fixed on the quarterback competition among Matt Cassel and Teddy Bridgewater — and, allegedly, Christian Ponder. But it doesn’t take Bud Grant to deduce that none of those three will be successful without the offensive line improving upon its erratic pass protection during last year’s 5-10-1 meltdown.

“When you watch this offensive line, and they are playing at their best, at a high level, then, yes, they are good enough for us to go have success,” Turner said. “We are trying to get them ready to win.”

Turner wouldn’t concede that his starting five are locked in. However, based on first-team reps this offseason and during the first three days of training camp, it certainly appears that the same five players — left tackle Matt Kalil, left guard Charlie Johnson, center John Sullivan, right guard Brandon Fusco and right tackle Phil Loadholt — are set as the starting five for a third consecutive season. If there’s any legitimate competition with a current starter, it’s most likely coming from rookie David Yankey at left guard and Vladimir Ducasse at right guard.

“From a communication standpoint, it’s huge not only having the same five starters but also having Jeff Davidson still in the room as line coach,” Sullivan said. “How we did last year is a question you’ll have to ask the coaches. But nobody has ever played a perfect game. We have to get better. But I have full faith in this group.”

Zimmer said he thinks it is more difficult mentally to play offensive line today than two decades ago. “And I’m proud of that, too, by the way,” added the former defensive coordinator who contributed to the advancement of the league’s evolution of exotic defensive schemes, disguises and fronts.

“That’s why everywhere on our football team, we love to have smart guys,” Zimmer said. “You can’t cover every little thing that’s going to happen during the course of a game. Guys have to be able to react quickly and think quickly on their feet. As I’ve said many, many times, a quote from Bill Parcells is, ‘Dumb players do dumb things. Smart players very seldom do dumb things.’ ”

Sullivan said quarterback is the most difficult position to play, “hands down.” Fullback Jerome Felton argued that it’s cornerback before adding that most people have no idea how mentally taxing it is to understand offensive line play at its highest level.

“You can’t just have five big brutes who run block,” Felton said. “You’ve got to have a smart center, and he and the quarterback must be on the same page because the protection calls and adjustments are vital.”

Protection calls at the line of scrimmage start with Sullivan and/or the quarterback identifying the “Mike,” or middle linebacker. Ensuing calls for slide protections, specific responsibilities and blocking techniques are based on that initial determination.

“And it’s not always the actual ‘Mike’ linebacker that you call out as the ‘Mike,’ ” Sullivan said. “You get to choose the ‘Mike’ based on what you think is going on with the defense and which call you think gives you the best possible position to pick up the blitz.”

Defensive end Brian Robison said he thinks offensive or defensive line is the toughest position to play.

“I do know as a defensive end, the toughest thing might be to sack the quarterback,” he said. “You may get 500 rushes in a season. And 10 sacks is a good year. So your percentages aren’t very good.”

Of course, when asked if he has ever played offensive line, Robison looked like a man being asked to eat a worm.

“I have never played offensive line,” he said. “And I have no willingness to do so.”