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Vikings linebacker Anthony Barr, defensive end Scott Crichton and offensive lineman David Yankey hit the field Friday for the team's rookie minicamp. But unlike the other drafted rookies, they will have to fly back to campus after the session Sunday because of an NFL rule.

UCLA, Oregon State and Stanford are on a quarterly session rather than semesters, so all three players can't participate with the team outside of the rookie minicamp until after their final day of exams if they haven't graduated.

Oregon State and UCLA have finals on June 9-13, while Stanford will have its finals on June 6-11. It interferes with team's organized team activities May 28-30, June 3-5 and June 9-12.

"I've got to go back on Sunday for about a month, so hopefully I can learn and hopefully they'll continue to send me stuff, send me film," Barr said. "It's going to be more mental than physical."

Crichton, Yankey and Barr all will finish school in time for the Vikings' mandatory minicamp June 17-19.

Under the collective bargaining agreement, the Vikings can contact still-to-graduate players on weekdays between 5-8 p.m. They also can fly out during the weekday to visit for instruction and video review, but no physical activity.

"It's a huge disadvantage," Crichton said. "Everyone else is learning, but at the same time I still get the plays they have to do, the clips of the practices on my iPad. That kind of helps, but the whole one-on-one thing with my coach [and] the vets coming in, too, that's a big disadvantage."

Crichton said he will video chat with defensive coaches Andre Patterson and Robb Akey, and Barr said linebackers coach Adam Zimmer will fly to Los Angeles.

"I want them to learn how we're lifting, how we approach the different techniques, the different coverages," Vikings head coach Mike Zimmer said. "And then the offensive line with Yankey, [it's] more about the techniques with him, play calls, the terminology, things like that; things they can take and go back to their schools and work on."

Jerick of all trades

Running back Jerick McKinnon did just about everything at Georgia Southern. Along with running back, he also played quarterback and cornerback.

But he wasn't a pass blocker. It's a skill McKinnon will need to develop as the team's third-down back and recently has started to learn.

McKinnon said the Senior Bowl was the first time he was used in pass protection, and it was a difficult adjustment.

"When they're coming at you, you get so antsy and want to fit up, but you've got to be patient," McKinnon said.

Running backs coach Kirby Wilson said McKinnon has high "block willingness." As McKinnon continues to learn the technique — vision, hands and feet — both believe it won't take long for McKinnon to develop into a good pass protector.

"He's got a certain amount of toughness to him where right now, the next level for him would be technique," Wilson said. "The toughness is there, the attitude is there. Players like him tend to develop rather quickly as a pass protector because of his [block] willingness."

Etc.

• The Vikings practiced outdoors with an emphasis on technique.

• Zimmer said he wants to see flashes and athletic ability from the undrafted free agents and tryouts participating in the team's rookie minicamp.

• When asked how it felt to put on a Vikings jersey, Barr said: "I look good, man. It was pretty sweet. So hopefully I'll be able to play as great as I look."