– Vikings running back Jerick McKinnon stayed after practice Sunday evening to work repeatedly on pass protection techniques until only a few teammates were left on the field.

Why?

We’ll give you three reasons.

No. 1: He’s young.

No. 2: He’s really inexperienced.

And, oh yeah ...

No. 3: Pass protection is really, really hard for an NFL running back. So hard that even Adrian Peterson isn’t great at it.

“It’s the most difficult job they’re going to have every week,” said Vikings running backs coach Kirby Wilson as McKinnon worked up a sweat nearby. “Generally speaking, the guy you’re blocking outweighs you by 30 to 50 pounds. He’s stronger. He’s bigger. And rushing the quarterback is what he does for a living.”

In this one particular area, Peterson doesn’t even rank No. 1 on his own team. If watching the 1-on-1 drills isn’t proof enough, there’s this from Wilson:

“Matt Asiata has been consistently our best pass protector,” Wilson said. “He’s pretty darn good at it. Actually, he’s outstanding.”

Asiata isn’t a natural pass protector, either. Then again, who is at that position?

“I think it’s pretty hard to learn coming into the NFL because in college they don’t really teach you how to do it,” said Asiata, Peterson’s backup. “Being a rookie free agent [in 2011], pass blocking was the key to staying on the team for me. It’s a passing league and somebody has to protect the passer.”

Pass protection probably will punch Asiata’s roster ticket again this year. As for Peterson, well, let’s just say he’s got other things on his plate. But even he knows he can’t be seen as a protection liability by defenders frothing to hit quarterback Teddy Bridgewater.

“It’s something Adrian wants to get better at,” Wilson said. “He feels like he’s just average at it and he wants to be great. So he’s working hard.”

Peterson was asked Saturday if he enjoyed the 1-on-1 pass protection drills since it’s basically the only contact that’s permitted for him in training camp.

“Do I like [the blocking drills]? No,” Peterson said. “But not being around football for a year, I feel like it’s something that’s going to be important for me to get back out there. We have a great group of linebackers, so going against those guys in pass pro 1-on-1s is going to be good for the group and for me to get back into the groove.”

The key elements of sound pass protection start with the proper and consistent width from the quarterback’s drop point. A square base with feet moving is needed to set up a two-handed jab or punch that must be well-centered on the defender’s chest and performed on balance with hips low and head and eyes up.

“And hit them before they hit you,” Asiata added.

Now go try all of that against a bull-rushing Anthony Barr and see what happens.

“It’s not easy,” Asiata said. “I don’t know if it’s underrated, but it shouldn’t be. If it’s a passing league, your quarterback needs to trust his protection.”

The Vikings running backs have struggled for the most part in the pass protection drills against linebackers during the first week of training camp. McKinnon has had a particularly tough time. That, of course, needs to change if he is to fulfill the team’s aspirations for him as a multidimensional third-down back.

Wilson said he doesn’t get too worried about the end results of the 1-on-1 drills because “they’re unrealistic.”

“When we’re running inside drills and the linebacker has so much space to run and jump around blocks, that’s not real football,” Wilson said. “So we don’t really get concerned about how a specific competition drills looks like. We worry about what our technique looks like.”

But Wilson does admit McKinnon needs more work.

“It doesn’t happen overnight,” he said. “He’s getting there and as you can see he has the willingness to want to do it.”