Jaymar Johnson practicing his way off the practice squad

MANKATO — Jaymar Johnson didn't want to say too much, but he left little doubt that he expects to win one of the Vikings return jobs this season after spending his entire rookie campaign on the practice squad.

"You're going to see during the preseason," he said this summer. "I'm not going to speak on it, but you're going to see during the preseason."

Johnson is making a strong bid in training camp to earn a roster spot as both a receiver and punt returner. He devoted extra time this offseason working on catching punts and even had punter Chris Kluwe kick to him a day before training camp officially started on an otherwise empty practice field.

"Jaymar Johnson is not a guy that has to be chased down to work," special teams coordinator Brian Murphy said Friday. "He had very clear goals going into the offseason and he's worked every day -- and when I say every day, I mean every day -- to accomplish those goals that he has in mind."

Johnson and rookie Percy Harvin are getting most of the punt return reps. Johnson seems more comfortable in the role at this stage.

"Jaymar looks good on punts," Murphy said. "He's put a lot of work into it this offseason. That's really a credit to him. He looks like a different guy. He's confident underneath the punt, he's fundamentally sound. We all know he's gifted with tremendous athletic ability."

By all indications, rookie Phil Loadholt will be the starting right tackle this season, which means Ryan Cook likely will become a utility backup capable of playing multiple positions. He is getting work at tackle, guard and center in camp.

Cook played center at New Mexico and said the transition back to that position has been relatively smooth.

"It's kind of like old hat for me," he said. "There's still things I have to learn at this level. But I played there in college for five years. I think the bigger learning curve for me coming in [to the NFL] was playing tackle."

Cook dropped 10 pounds this summer and entered camp at 316 pounds.

Running back Adrian Peterson said he begins every season with an individual goal of rushing for 2,000 yards. Offensive coordinator Darrell Bevell doesn't see why that can't happen at some point.

"He's been hovering around that area so I'm not going to crash the man's goals or his dreams," he said. "If he got 2,000 yards, we're doing something right. There would be a lot of happy people. Do I think it's possible? Yes."

Several NFL officials visited camp to brief the team and media on new rules changes and points of emphasis. One of the most significant changes is the elimination of wedge formations involving more than two players on kickoff returns.

It has been common for teams to use three-man wedges -- typically offensive linemen -- who link arms to form a wall of protection. The NFL decided to prohibit that tactic because of the number of serious injuries, notably concussions, suffered by players assigned to break up the wedge.

An illegal wedge is now defined as three or more players lined up shoulder-to-shoulder within 2 yards of each other. That will result in a 15-yard penalty at the spot of the wedge.

"It's truly a 1-on-1 game now," Murphy said. "It will be interesting to see, but I'm not so sold that even a two-man wedge is any better than a single block as far as guys being able to avoid it and bend back and make plays. It goes back to personnel. Is the offensive lineman still going to have a role in that or do you need more athletic guys because the surface is smaller? It will be interesting to see how that all kind of evolves."

• Referee Tom Barnes said offensive holding is a point of emphasis for officials this season. "We missed a number of offensive holding calls last year," he said.

• According to league data, from 1999 to 2008 the Vikings had the second-most challenges in the NFL with 82, trailing only the Denver Broncos at 90. The Vikings had 27 reversals.